Right, I got to thinking about that. A few sites that reviewed the 6870 showed the power consumption of 2x in Crossfire being around 390 watts in "benchmark systems", so I imagine this in case, running the Sempron buys me some overhead but that's too close for comfort. I'm thinking a 480w CoolerMaster would put me in a safer range... but it's not certified 80+.

I guess basically the point to my original thread was that when running a GPU rig, the CPU really doesn't matter. If anything, spending money on CPU for mining is pointless as the cost for performance between CPU's and GPU's is ridiculous:

~18 Mhash/sec for i7-980x ($1,099)
~300 Mhash/sec for 6870 ($199)

So for others that might have asked in this thread, I would say that any money spent on a CPU that's greater than a Sempron is just money wasted.