However, since you have a AMD based system, why not a 3870? They are cheaper, and produce a better picture quality. Not to mention that they over clock like crazy with the stock cooler.
I know the 512 version is better but will I really see a big difference in frame rates between the two when i play high setting no aa or af? I don't what to go with ati because i hear about them having driver problems alot and i like to play around with Linux witch doesn't have any good ati drivers. and i am probably going to upgrade to an Intel 8400 45nm dual core system in a couple of months.
It depends on resolution. At lower resolutions cards with less video memory will perform about the same as cards with more video memory. However, once you start climbing in resolution cards with higher video memory will outperform cards with less video memory.
For all those games, you'd be bonkers to get the 256MB version, they fall way behind in modern games, and at higher resolutions they crash, they simply can't play the games at all at certain specs (which gives you a problem as you've got to try and set the resolution back without the game crashing!)
I would never buy a high end card with that little RAM these days.
Even older games like Quake 4, the 512MB on my card is barely enough.
The 8800GTs have been out of stock for a while, they're so popular the manufacturers can't keep up with demand. By the time they come back in stock the price usually rises.