Looking on Newegg, the eVGA 8800GTS 640MB card is $350 after rebate, and the ultra-OCed 320MB version is $330. Essentially, there is no difference in price.
Which one is better?
I know the 640MB one is going to help if you are running a high res monitor (like 1680x1050 or 1920x1200) due to the extra RAM. However, is there any situations where the OCed 320MB version will be faster (say you are using a monitor at 1280x1024)? Will the extra RAM in the 640MB do anything over 320MB at low res?
The 640MB version is running at spec, and I am sure you could easily overclock it yourself by say, 10%, and come close to matching the GPU/memory speeds of the 320MB version - but again, are there situations where the 320MB version will be faster?
$20.00 for 320 megs of video ram added on !!! DUHHHH ..... ya can't buy it for that in any form ... and it can't be added .... get the 640 ! In the future the extra ram may be alot more useful than resolution .... who knows . What alot of these guys don't tell ya is if your monitor can't do those high res factors what do you need a card for that does them ? Or any descent priced LCD will probably never do them . But I'd give 20 bucks for 320 megs extra any day !