Just to add... I built this thing 3.5 years ago....at the time it had a XFX GTX285 which sucked a fair bit of juice...
Now it's running a ASUS GTX590 which sucks a 'tad' more..... but it was not going to be an issue [for me] as I'd opted for an Antec TruePower Quattro of 1000w.
Since then I also went from 6g to 12g ram....soon to be 24g [max for the mobo] and drives have increased in both number and capacity.
All things being equal this box should kep me happy for anothr 3 years at least...
OK, so 3.5 years of almost continuous use and the CPU cooler fan died...but since replaced with a better quality ver ...