wow it would be amazing to find the 320bit (older) 8800gts for that price... let alone the newer g92 based GTS.
From what I've read, the g92 based 8800gts is OVERALL better in performance than the older 8800gts.
(Even the 8800gt (g92 based) in this review destroys the old 8800gts
http://www.anandtech.com/video/showdoc.aspx?i=3140&p=7)
Even with anti-aliasing, the new weaker and renamed geforce 9600gt (aka 8800gt but slower) beats the 8800gts 640mb (old g80).
http://en.expreview.com/2008/04/02/g80-vs-g92-hi-end-geforce-gfx-cards-round-up/?page=10(my power supply is some 500w with (i can't remember) less than optimal amperage for my 7900gs, yet it's been working for awhile? technically if you can run the 8800gt, you should be able to run the 8800gts (g92 versions) as they are based off of the same construction/pcb though manufactures are usually trying to be safe about it)
I would personally go for a g92 based card definitely.