Is there any real requirement for more than 512MB of GPU memory?

I'm not really seeing any amazing deals on NCIX.

No, not really. You would need a more powerful GPU and a higher memory bandwidth to make good use of more memory.

That depends. If the games uses a lot of textures (like some of the Oblivion graphic mods), it helps to have a lot of memory around. Otherwise, currently I'm seeing 512 MB on the recommended side of new game requirements (thinking of Dragon Age specifically).
Edit: What Xenitis said also applies.

THIS is actually the machine I'll be upgrading. Does anyone see any potential issues with the chosen PSU, or the suggested GTS 250 video card?
Contrary to what the specs say, the x16 slot is open.

Just make sure they'll both fit. My vid card is pretty large: it occupies two slots (width) and is pretty long. I had to cut parts of the frame for my Dell XPS to make the PSU fit. Granted it was only an extremely minor change, but it will really depend on the inside of your case.

Hmm, I just assumed the PSU compartment was suited to standard ATX...
EDIT: Popped my case open, and I'm quite certain my PSU compartment is indeed standard ATX, and I think the GTS should fit, as that section of the case pretty much has space from the front of the case to the back, and the x1 slot is next to the x16, so I should have space for the "doublewide" card.
Hmm, the 40nm does sound interesting, and the 4770 is actually on newegg.ca for $120. Doesn't come with any games, but realistically, I already have CoD4 and WaW for my PS3.
The smaller size, and lesser power consumption are sure pluses.
Performance on the 4770 is comparable to the GTS 250?
Any comments on these manufacturers?
http://www.newegg.com/Product/Product.aspx?Item=N82E16814141098
http://www.newegg.com/Product/Product.aspx?Item=N82E16814131155
http://www.newegg.com/Product/Product.aspx?Item=N82E16814161279
The HIS (Never heard of them) Seems to offer the longest warranty.
EDIT #822:
Does ATI have anything like CUDA from Nvidia? I'm quite interested in physics performance as well.

The smaller manufacturing process not only saves power and means cards can be smaller, it also leads to a reduced heat output. This means even a powerful card will run quite cool and quiet with the stock cooler, even if you have it slightly overclocked (some cards ship with a modest factory overclock to take advantage of this). The same gains apply to Intel's later Core 2s and all i7s.
Developers haven't really taken much advantage of CUDA; they often use PhysX, however, for which only Nvidia cards include hardware acceleration because Nvidia makes and owns PhysX. Other physics systems, such as Havok, do not have any hardware acceleration at the moment.
Microsoft is incorporating GPGPU functionality into DirectX 11 in the form of "compute shaders"; this allows cards to perform non-video tasks, just like CUDA, except it works on cards by any manufacturer. I suspect that once developers start taking advantage of DX11 they will use compute shaders rather than restricting their games by using CUDA, although PhysX will probably continue to only be accelerated on Nvidia cards. It's also possible that PhysX will fall in popularity at this time if it stays restricted to Nvidia, especially if Havok and the like start using compute shaders for manufacturer-independent acceleration.

Ati's answer to CUDA is "Ati stream".
I've read some reviews and it seems they are pretty equal. Performance looks almost the same. Both cards have lowered power consumption.
As for manufacturers - 4770 - all seem the same. GTS250 - I think Asus model with it's "dark knight" cooler - it has nice feedbacks that this cooler is less noisy.
Actually right now I'm choosing between these 2 cards too.
I think I'll go for GTS250 - it's easier to find, because 4770 are not in stock here, and I heard there were some problems with 4770 because of bad cooling on power elements.
There are a lot of comparison reviews and test of these 2 cards so you can find info very easy. )

Benchmarks I'm seeing rate the GTS 250 slightly higher than the 4770, but it costs more, and draws a lot more power.

It's specifically the PhysX support that has me interested in Nvidia, because, based on videos I've seen, the difference is quite "night and day".
Do all CUDA enabled cards have the capability to run full hardware-supported physics, or are these demo videos still showing simulation running on a dedicated physics unit?

CUDA-enabled video cards actually have faster PhysX processing than the dedicated cards did, and this will only improve over time. Because PhysX is handled as a separate API all PhysX-enhanced games can have full hardware acceleration with an Nvidia card, even those that were released before Nvidia cards supported PhysX.

Faster, eh? I was really leaning toward that 4770, but PhysX support is actually a pretty big deal to me... and since I made the mistake of pricing the 4770 on newegg.com, rather than .ca, the price was inaccurate. the GTS 250 is only a few bucks more...

Well, I just ordered the 512MB XFX GTS 250, and a 630 watt 80+ rated Rosewill PSU. The PSU was some deal of the day thing, and only ended up costing like, $2 more than the 430 watt I had in my cart.
Depending on where Newegg.ca ships from, I should be doing a lot more PC gaming this week. :)
Thanks for the help and advice, everyone.

Sounds like a good deal on the PSU. Always nice to have some extra watts available.
Let us know how the upgrade works out for you :)

Parts arrived yesterday. So far, I'm quite pleased, everything went together with no issues, aside from a slight size problem with the video card. Nothing big, it's just pushing on one of my SATA connectors on the motherboard a little bit.
Kinda surprised how much heavier the new PSU is though..
The important part, is that I can now play games, even Crysis, and ArmA II. Though I seem to have some strange, random input lag issue with the Crysis demo...