8GB is good. You want something more than 4GB, and 8GB is the next easy step up.

There are not many compatibility issues, so long as you get RAM that is of the same type that the motherboard takes. Virtually all new motherboards take DDR3 in the form of 240-pin DIMMs (often called "sticks"). You will do best to buy them in kits of 2, such as 2 x 4GB (makes 8GB).

One known compatibility issue is that MSI "B3" motherboards seem to dislike G.Skill-brand RAM. So avoid that specific combination.

Corsair "Value Select", Kingston "ValueRAM", G.Skill "Value" (except on MSI motherboards), Crucial "Value", Mushkin "Value", Patriot "Value".

Don't overspend for fancy heat spreaders. These just look pretty, drive up the price, and get in the way. RAM is cooled through the leads, more than through the air.

Alright, so far I have several potential componenets picked out.

CPU: Intel i5-2500 210USD
or
Intel i5-2500k 230USD

Video Card: msi Geforce GTX 560 Ti 2GB 270 USD
or
HIS Radeon 6950 2GB 270 USD (It said it has a special cooling system that keeps the temperature lower than other cards.)

Monitor: Asus LED backlight 190 USD
or
Asus full 1080p LCD 180 USD
or
Asus LCD 170 USD

Power supply: Antec 750watt 100USD (I'll have to check more on power supplies. I still don't know much about their differences.)

Once I decide on these things, I guess I can pick out a motherboard and case.

CPU: The difference between the i5 2500 and 2500K is overclocking. "K" CPUs can be overclocked; non-K ones are designed to frustrate overclockers. Worth $20 to you? I don't know.

Video card: 2GB hasn't proven its worth yet; you can save $50 or so by going with 1GB. If you're going with an MSI or HIS card, get one with their proprietary coolers. The MSI "Twin Frozr" and HIS "IceQ" cooling systems are both excellent.

Monitor: Try to go around to brick-and-mortar stores to see these monitors in action, too. Those are TN monitors, which are fine if serious digital photography is not among your hobbies.

Power supply: Picking power supplies is a minefield. The market is full of companies that don't make their own power supplies, but buy from a smaller number of more or less reputable manufacturers. For reasonably priced power supplies, Antec, Corsair, and Seasonic are your best bets. Avoid the Antec "Basiq" series; other Antec series are OK. Any Corsair or Seasonic is OK. 750W will run pretty much any CPU and two GPUs out there, but 650W or even an excellent 500W supply is enough to run what you have specified now).

if you do plan to upgrade in 2-3 years, then go for the 750w psu. Just make sure the ripples are not to numerous and that it provides good, consistent performance at high loads. You won't ever hit 700w with your rough list of components, but it's always good to have a high ceiling for over clocking, if you ever wish to pursue that area.

2GB VRAM seems to be a little overkill, since game like B3, Serious sam 3 and skyrim (with mods) use quite a bit of memory but are in the minority. Shoot for a 1.5gb card since playing at 1080P will most likely maximise the VRAM in future games.

Get the 6950 if you DO wish to go down the AMD route. Simply because you can flash it to become a 6970 with a well documented process, upping it well over the 560Ti. Which is still a excellent card, but you can't flash it to a 570. ;)

The displays are ok, to be honest even though IPS panels are expensive (well most) the added clarity, colours and overall increase in quality compared to dire TN are easily worth the money. Since this is your first ever gaming pc, go down that route.

To add some to CJ's post...
A note to add to this many new MB's come with overclock switches or buttons that do a slight automatic overclock for you Here we disagree slightly 2GB lets you play with better AA and at higher resolutions than 1GB, games are already GPU memory bound at 1GB some are even at 2GB if you like your eyecandy VRAM is already a limiting factor. If you go 3d or multimonitor later on more VRAM is a must. yeah pretty much if you don't care about colour accuracy TN is fine For a 2500(k) with a single HDD,GPU and optical drive 500W should be fine
oh god you kill me Mushy... for the first see above 2GB is pretty nice nowadays 1-1.5 is limiting NV cards hence the release of 3GB cards lately
And the second point is about a year outta date doing that to most 6950's now will leave you with a dead GPU

*Pokes wodmarach since he is apparently dead, shoots me a right dirty look*

Ah! The angels haven't taken you yet! ;P

Going onto my point of 1.5 cards, I mentioned that future games will most likely maximise VRAM usage, you mentioned the advantages of more, I agree with you after reading your post and hope he gets the 2gb version of any card.

Oh, and I never knew about the second point, stopped following 6 series news after reading the flashing news. Thanks for correcting me since it would be gutting if the OP tried to flash his card and ended up with a super expensive, super large door stop. :)

Tbh the 6 series is probably now ignorable if planning for the next few months the 7xxx series is hard released the 7970 is out we're just waiting on the slower chips now the last of which is due out april apparently... the 5xx series from NV is around a little longer as their next chip isn't expected to even paper launch till then.

"Tbh the 6 series is probably now ignorable if planning for the next few months the 7xxx series is hard released the 7970 is out we're just waiting on the slower chips now the last of which is due out april apparently... the 5xx series from NV is around a little longer as their next chip isn't expected to even paper launch till then."

But the 7000 series will be extremely expensive, and if everyone is correct when they say that a 6950 or 6970 can play BF3 and The Witcher 2 fine, than that's fine with me. Also, by the time I get the money for this, the 7000 series might be out and the 6000 series might be alittle cheaper.

About the monitors: where do I find whether or not they are IPS or TN?

I don't think you have to worry too much about the video card. I built a super budget PC but I set pretty much everything in Witcher 2 and in BF3 on max.

I had a 3 core AMD "Rana" chip. It was $70.
Motherboard was less than $100. Cheapo ASRock M3a770de. Super cheap thing.
I only have 4 GB of RAM.
I paid about $160 dollars for an HD 6870 1 GB which can play these games at very high/maxed quality at 1080 resolution.

So pretty much, your computer should be fine as long as it's better than my specs, which isn't hard.

The only thing that's disappointing is that the Skyrim HD textures mod causes my computer to stutter a little bit, but I'm not sure if it's my card, my CPU, or my RAM, or what.

I haven't quite figured out the code to quote properly :P

Yes I figured it was my GPU, but I was sort of dreading it because it's the hardest to upgrade in terms of $$$. I just got an SSD because I had been running with a 7 year old IDE hard drive to save initial cost.

The maker of Skyrim HD claims to use a 1.25 GB card just fine, although an Nvidia that's a bit better than mine. I was hoping that the difference wouldn't be in that 0.25 GB.

It's actually a fairly large hit have you dropped AA and AF to nothing and tried it?

No I totally forgot to set my graphics down lol!

I had all the sliders set to max I believe. I'll have to try it. You have a suggestion to reduce? Maybe draw distance?

Funny enough, my GPU just died on me too. It was a Sapphire, so I'm sending it back tomorrow.

Edit: I see you mentioned AA or AF. I'll mess with those when my GPU gets back to me.

IPS monitors are never cheap. Their price has come way down recently, with a few under $200 street price. LG probably sells the most, and they make many of the IPS screens that other manufacturers use. HP, Dell, NEC, and others also have IPS models. Apple Studio Displays are all IPS.

Here's a reasonably recent list of IPS monitors: http://www.pchardwarehelp.com/guides/s-ips-lcd-list.php

A note to add on selecting a power supply: look to get one that's modular. This means that most of the power connectors can be detached from the PSU if you're not using them so that you don't have a big mess of unnecessary cables cluttering up your case. This goes doubly so if you go with a mid-tower case and not a full-tower.