8800 GTS in a Dell Precision 390 with 375w PSU.
I don't remember the exact watts drawn by the 8800 GTS, but it was about 5w more than the biggest power drawing Quattro that Dell offered as a standard upgrade for the Precision 390 and about 8w less than the dual Quattros offered in the Precision 390. I figured Dell would not risk $1000 worth of Quattros for 3-5 years (business class warranties) if the PSU was undersized. There are guys all over the Dell forums that had done the same, so the safety in numbers reinforced my thought process.
That was 1 year ago. Still going strong with Q6600 plus 4 HDs.
Bottom line, Dell seriously underrates their PSU's using sustained power rather than peak power like the PSU manufacturers. BTW, HP is just like Dell. The HP workstations have the same "crappy" 375w PSU with identical Quattro card selection.