what resolution are you using? Most are based on the reference design and should be fairly similar so the choice is up to you. The difference is mostly in quality control, warrenty, and bundle. Evga is generally considered on of the better brands.
At this point in time, I would chose one of the 640 cards. Games are becoming more shader intensive and will need the extra memory. FEAR and GRAW are examples. Crysis is another. I think, even on a crt running at 1024x768 with the goodies turned up, a 320 card will choke. If the quality at which you play doesn't mean anything, get the latter. A wide screen lcd will also need the extra memory.
As for vendors, a few distinguish themself like XFX with their double lifetime, so if you sell it, its still warrantied.
Other then that, look at the Price/bundle/cooler/warranty and make the pick on what's most important for you, they're essentially the same...
Anandtech had a few roundup between the makers, nothing spectacular came out of it..
hey guys thanks for the feedback, a bit more information
my screen i am going to have to use will be a 32" lcd tv with a 1366 x 768p
in terms of the 640mb card my system price is already rocketing. initially came on here saying i was going to get the 7900 card. since been convinced i need to have the 8800 gts, not really sure i can go up to a 640 mb card unless you lot in the know insist its really worth the extra cash.
also im going to buy a E4300 and oc it to 3.00ghz will this processor start to become a bottleneck for such a great graphics card?
i have the evga 8800 640 and it rocks- and no that cpu will not be the bottleneck- the bus and HD will be the soft spot which at this time there is not much to do till the next round of chipsets get out. not sure if P35 is any better as it's so new.
but anyway the 8800 640 owns and evga and xfx are the best vendors and worth the few extra bucks (quid)
the 640mb version isnt worth it as the price is so close to the gtx. i have the 320mb version and it plays my games perfectly at max settings 1440x900 res. i recomend playing on a monitor because having 1330xwatever you said on a 32" wont look good