My 750w will go into my next more with the times as some members have pointed out computer. pci-e 8800gtx X 2 duo core cpu and all the other bells and whistles that require POWER.
Anything less and your hanging on for dear life and doomed for a KABOOM
I agree whole heartedly it might be a little overkill and I say might NOW
But I'm also thinking about the future. And 400w ain't even going to turn it on.