So I Stuck my Toes in the Pool - 8800 GTS 640MB

I'm still running my P4 3.8 machine with an Ultra 500W and BFG GeForce 7900GTOC card. Tigerdirect had a good deal on a PNY GeForce 8800 GTS 640MB GDDR3 PCI Express SLI Video Card coupled with a Ultra X-Finity 800-Watt SATA-SLI Ready Power Supply.
Am NOT moving to V$sta for at least another 6 mos if not longer. I believe sales are not going to be anything close to what even their lowest estimates were, and that will cascade down and across to all the retailers for all the new stuff one needs to run V$sta. I expect massive discounting, especially with the housing-induced recession we are entering. So, that extreme edition or even quad-core may not be quite so out of reach in about 6 mos.
However, that being my plan, I and sticking with XP for the moment and won't get the DX10 eye candy for now, but I figured the video card would still be an improvement over what I have. And, I will need, eventually at least, the higher power supply. Should I put it in my current unit because I hear these cards suck a lot of juice and something about the rails (which I don't understand)?
Anyone else purchased one of these cards and installed it your (Intel) XP machine? How did it do?
Am NOT moving to V$sta for at least another 6 mos if not longer. I believe sales are not going to be anything close to what even their lowest estimates were, and that will cascade down and across to all the retailers for all the new stuff one needs to run V$sta. I expect massive discounting, especially with the housing-induced recession we are entering. So, that extreme edition or even quad-core may not be quite so out of reach in about 6 mos.
However, that being my plan, I and sticking with XP for the moment and won't get the DX10 eye candy for now, but I figured the video card would still be an improvement over what I have. And, I will need, eventually at least, the higher power supply. Should I put it in my current unit because I hear these cards suck a lot of juice and something about the rails (which I don't understand)?
Anyone else purchased one of these cards and installed it your (Intel) XP machine? How did it do?