dont be fooled by the 6600GTs high clock speeds... its not a bad card, but it is no longer the best bang for your buck.
the 6800nu at stock speed 325/700 out performs the 6600GT 500/1000.
its because the 6800 has 2x the bandwidth, with 12piplins 5shaders... witch can be unlocked in some casess to 16/6... even not unlocked the 6800 is better. Iv ran them both.
the "6800 128mb" at $165 after rebate will outperform the "6600GT 256" at $200.
Its priced higher because they can sell it to all the noobs who see a higher clock speed paired with 256ram.
EDIT: iv ran the 128mb 6600gt, but the extra 128mbs wont add that much performance, if any at all.
i got a 6600GT 256mb....works fine for me the main reason i got the 256mb one was cause it was only $2 more than the 128mb one i paid $300 for mine (keep in mind im in Australia) but i paid this quite a while ago now....
Well if you're going with a 6600GT, just go with a evga, leadtek, gigabyte, or chaintech. Don't go with a 256Mb, as you can buy a 6800GS off newegg for relatively the same price.
256mb is a waste of money, you only get around 5 fps more for a lot more $$$. Those 6800GS sound promising but i dont think he has a PCI-E slot because of the 9600XT. I get a 6600gt or a 6800gt if you can afford it.