Well just a sec, first of all, I never said I have a 7800GT, right now I have some crappy Radeon X300. My psu Is a 360W with 24A on the 12V and I have been told repeatedly on these and other boards that it would be enough to handle a 7800GT because the only other things I have connected that would drain serious power are my cpu, two optical drives and one harddrive. I also went to the PSU calcultor site and with everything my comp has in it, it uses about 315W with with the CPU at 100% utilization.
I wasn't looking to buy something like the X1900XT because they are simply too expensive. That's why the 7900GT for 300 sounds really good to me.