I've been researching the possibility of getting an 8000 GTS 640. THe price differences between brands is quite large so I was looking at the cheapest(as far as I know)PNY 8800GTS 640 MB versus the dearest which seems to be the XFX or eVGA brand.The question is: What are the fundamental differences between 2 versions of the one card. From looking at the specs I can't deduce what's better (or worse) for the $.

There's virtually no difference between brands. + or - 5%, max. The most important difference is the warranty. Examine that carefully. These things do break.Nvidia will have a new Vcard that will triple the 8800's performance in 2-3 months. A strategy might be to get a decent 7-series card and wait for this new "G92." Hard to give up a triple (for the same price) just a couple months away.