I agree with Mike, that PSU is horrible.
It's the only component beside the GPU that actually matters for 24/7 use.
Spend the extra for a quality one, skimp on the RAM and processor.
He said "cheapest hardware".
That was not the cheapest PSU. That PSU is actually quite good, there were cheaper options.
Those cards run 108 watts max load. With a 45 watt Sempron, two 5770s that's 261 watts (cpu is unlikely to be under full load). Add in the motherboard, ram, HD, 500w is plenty. He'd never even hit 300 watts. You could even run 3x5770 if you wanted to really push it.
Since he said "minimum/cheapest" setup, I'm quite happy with my suggestions. =)