The best bang for the buck is with GPUs. Hands down. Get yourself a good x6 core AMD or x4 core i7 CPU + a mobo with 2 or 3 PCI-e slots that both run at 16x speed. That won't break the bank - easily done for $350 to $400. That's all you need. The exotic stuff is just going to waste your money if you're after credits - let's all be honest.
Throw your $$$ at the PSU (which you just did!
), and GPUs. Get 2x the dual cards - either (2) NVIDIA 590 or (2) AMD 6990 GPU cards, so you effectively have 4 GPUs. You will easily have a rig that crunches well over 1Mil per day... on 1/2 your budget.
If you really want to spend $6K to help out the team ... BUILD 2 OF THESE MONSTERS!