Hrmm i perfer eVGA, read alot of good things about the card. In addition its one of the cheaper nivida cards on the market. I have read of no complliants about the cards but if you are goign with the 6800 series just make sure you give the video cards its own power line from the psu. People have been having problems with their 6800GT's where they are using a power lines splitter to power their 6800GT's which causes problems if you do.
With a quick look at your specs, (if you are using that system for gaming) i dont think you have a fast enough system to run the lastest generation of cards. I really think that your cpu will be a bottleneck and 256MB wont really cut it if you are looking to game with games like hl2 comming out. You might want to look towards a 9800pro an extrmeley good card and really cheap. It really close to the performance of the 6600 series and x600 seriers cards out there. Plus you can get teh cards for like $150. Saving you some money to upgrade your system when it comes time to.