I would have thought there was a significant difference in power draw between 3 GTX295's and 3 GTX285's. I'm not too sure about the power consumption, but 6 gpu's vs 3 sounds like a huge difference in power requirements.
UPDATE on my 9800GX2:
Ever since I changed the TIM on the 9800GX2, seems like the EUE's have subsided for the most part. Still getting the occassional one, but I get those on both my other cards too once in a while. I just went into the other room to check on the folding status, I got kinda worried. The temperature in the room was pretty warm (felt like at least 25-29C) so I checked on the 9800GX2 temps. It now isn't budging a single degree over 80C! And, I've also noticed that yesterday it was in the mid 70'sC but what's interesting is that the fan no longer runs at 100% all the time. Hovers between high 60%-80% most of the time to maintain temps. All in all, one of the best things I could have done for the GX2!