Does it make much sense to build a dedicated GPU rig at this point in time?  I calculated a simple payoff of 5 months (which sounds good) for a rig that I'd build, but with BTC difficulty increasing at 10%/week it looks like it might never pay itself off.

Thoughts?

Also while I am posting, is a 650W gold PS enough to power a rig with 2 7950's?  (my current 7950 appears to draw ~200W).  I think the extra 200W should be enough to power the rest of the PC components...