I'm planning on building a gaming PC in a few months after I save some money. I was wondering what kind of video card to get. I know that the ATI Radeon 6990 is just about the best out there, but would two cheaper cards be better? Would two 6950's perform better than one really expensive card? Or are the Nvidia cards better than ATI? I really don't know much about video cards, so any help will be appreciated.

I would never recommend SLI / crossfire. It's very inefficient. If you really do insist on the best then go all out on a single card instead.

But again I have to wonder if that's really necessary. On a bang for buck basis most people recommend, with good reason, the Nvidia GTX 560 Ti. It doesn't really matter what brand, but I'd avoid Zotac as their fans seem a lot louder than normal.

So either get a GTX 560 now. Or wait and see what the next generation of Nvidia & AMD cards bring later this year. But I can't really offer a time frame on that. "This year" could still mean many a month.

Just as Navagon said, don't mess up your experience by trying to start out with SLI or Crossfire. Three times the hassle, twice the cost and power, maybe one-and-a-half times the performance.

The best values right now would be the GTX 560 Ti from nVidia (which is not the same as the GTX 560, just to make life more confusing), and the HD 6950 from AMD. Anything below those cards is a big step down.

If you wait a few months, you will get to decide between those and the new-generation cards (AMD 7000 series, nVidia 600 series).

But in any case, you will also need to be careful in selecting your power supply. These cards are little supercomputers, and they want lots of power, around 200 watts just for the card.

SLI / Crossfire adds between 10-20% performance AFAIK, so no, not worth it.

Thanks everyone. I don't really know what terms like SlI, Crossfire, or overclocking mean, so I guess I'll just go for a powerful, single card. Keep it simple lol. Like I said, it's going to be a few months, so I'll probably keep looking.

"But in any case, you will also need to be careful in selecting your power supply. These cards are little supercomputers, and they want lots of power, around 200 watts just for the card. "

By power supply, do you mean motherboard, or what kind of outlet you plug into?

There's a component of your computer called the power supply. It's what you plug the power cord into, on the computer side. If you open up the computer, you will see a large metal box with a number of heavy cables running from it to all the other components (motherboard, disk drives, etc.).

That's the power supply. Its purpose is to take the AC power from the outlet (110-120V in the US) and step it down to the closely regulated DC power (at 3.3V, 5V, 12V, and some others) that the motherboard and other components can use.

Many first-time build-it-yourselfers (whether building a new PC from scratch or upgrading an existing PC) neglect the power supply and end up buying a cheap piece of crap that fails soon after the computer is first powered on (and sometimes ruins an expensive motherboard or graphics card with it).

If you have any trouble identifying or understanding the purpose of any major component of your computer, you should seek experienced help when specifying, buying, or assembling a computer for the first time.

Going for an absolute top-of-the-line card like a 6990 means you'll be paying an absolutely ridiculous amount that is in no way commensurate with the actual performance increase you'll be getting compared to slightly less powerful cards. Having recently built a new computer for myself I can tell you that the 6950 is an excellent card that is running everything I throw at it with ease and barely breaking a sweat. A card like that should last you quite a while, then if you do eventually find that it's not quite meeting your needs you can look at upgrade options (by which point a new generation or two of cards will have come out, and subsequently dropped in price).

Also, I will reiterate what cjrgreen said about power supplies. A PSU is probably the number one component in a high-performance PC that you don't want to cheap out on (as if they decide to go out they can do so spectacularly, taking a few additional components with them). For a gaming PC with a single high-end graphics card I'd recommend a 600+ Watt PSU, and be sure that it's from a reputable supplier.

And again, to reiterate some of what's already been said, if you find yourself a bit overwhelmed by the various components you'll need to get and what specs to look for in each one, ask for help. There are many very knowledgeable people both here and on numerous other forums that are typically quite eager to help people select what components would be best for their needs when putting together a new PC.

Right now the 6950 is probably the top pick for a GPU on the Radeon side of things once price/performance ratio is taken into account (6970 and 6990 will get you more raw power, but the increase in price far outpaces the increase in performance). I'm not fully up on what Nvidia's line current looks like and what card looks best there, but someone else can probably fill you in on it. For CPU a Core i5 2500K is arguably the sweet spot on price and performance (the i7 2600K will get you a bit more power, but again the price increase outpaces the performance increase). To relate this back to what you're looking for, I put together my current computer a bit under a month ago with a 6950 and an i5 2500, and it's able to run The Witcher 2 at max settings pretty easily.

Cool. I'll probably go for the 6950 or GTX 560 Ti or whatever then. I also really want to get GTA 4 for the icenhancer mod. The video's I've seen of it just blow me away. Plus, my xbox copy is scratched up and I'd like to play through the story again.

SLI/Crossfire is fun to do, once, but as others have said it's expensive for less gain. Unless you're going to Crossfire two 6990s then there's no point, again, except just to say you did once:)

The main use of Crossfire or SLI is when you have a card that was once top-of-the-line but has been overtaken. If you can get a mate for it at a good price, and your motherboard supports it, you can set them up in Crossfire (ATI/AMD cards) or SLI (nVidia cards) and get a performance boost for a fraction of the cost of a new top-of-the-line card.

For new designs, get a single card that's as good as you need.

Okay, so Crossfire isn't worth it with the 6000 series right now, but in two to three years I might find another cheap 6950 and get a performance boost that way.

In theory, yes. But nothing guarantees that in 2-3 years you will be able to find a card that is fully compatible...

And, besides what has already been mentionned here about crossfire / sli ( modest increase in perf, large increase in power use ), be aware that multiple card solutions do cause problems related to heat management. Just check the thermal readings here : http://www.hardware.fr/articles/813-5/temperatures.html. Even if the text is in French, the pics are pretty obvious ...

edit : as you can see, dual card systems create a halo of heat that contaminates the CPU and the RAM modules. This may cause loss of performance or even crashes if you don't compensate it with better cooling systems.

That's right. Be sure to get a Crossfire-capable card (most, but not all, of them are) and a motherboard with a second PCI-Express x16 slot. Most better motherboards already have this. If the card comes with a "Crossfire bridge" (little ribbon cable that connects two cards across the top), be sure to save it for when you need it.

To minimize thermal problems, even with one 6950 (it runs pretty hot), get a large "full tower" case with plenty of ventilation and places you can attach large fans. Then don't worry about Crossfire until you get a chance to pick up a 6950 for little money.
I'm suspicious of the quality of the cooling setup in that article. It shows the 6950 running much hotter, even in the single card configuration, than others report it running at full load. It should be running in the 80's, to 95C peak.

But your point is well taken. You want a GPU with a good cooler design, a case with lots of room and plenty of airflow, and ideally not much cross-flow between the GPU and CPU. (Those and the power supply are your three big heat producers. The power supply has its own ventilation. The GPU and CPU cooling should be arranged so that hot air goes directly out from the case.) This is true whether or not you are running Crossfired cards.