i m so confused i have got 4 options here evga 9800gx2 overclocked , zotac gtx 275 .zotac gtx 260 i am having a 8800 gt right now and i have xfx 750i motherboard should i buy another 8800gt or i should be switching with any one of them which i have mentioned above please help me
If you have all those cards then go with the 9800GX2. If an 8800GT is the only card you have, then I would just buy a second 8800GT and run them in SLI. Know that there are some support issues with the 9800GX2 simply because nVidia didn't support it too long after they launched the GTX 200 series. Of course, they aren't exactly fixing issues for the 8800GTs now either, but they should give you less issues and it should be cheaper .
All of them will work fine in your system. ATI will always have the best price/performance ratio, but Nvidia has the stability and good customer service.
So I bought a GTX 275 for myself last year and it was really good. I recommend it to everybody.