go on, go find one. most benchmarks using stock 8800Ultra, which are overclocked 8800GTX.
im no fanboy, but the hassle of reinstall Windows and 0 power saving, along with same amount of heat being dumped into room. and worse folding performance, i think keeping 8800GTX is a better idea.
but if buying new cards, there is no reason to get 8800GTX. 4850 or 4870 is a much better choice
reinstall windows??? lol
the amount of time you've spent typing posts in this thread would be more than enough to clean the nvidia drivers out and install ati's.
4870/4850 with working powerplay most likely consumes less than a GTX in idle also.