You'll want to make sure to grab an i7 with at least 32GB of ram
And make sure the RAM is ECC; that's essential.
I have a mining rig that has two hex-core Opterons w/ 12GB of ECC RAM and RAID
4x PCIe slots, unfortunately I can only really use two of them... but mining on it is sort of its secondary purpose.
It's interesting though, in removing a CPU (and its RAM) it shaves only about 35W off of the idle power.
I need to post pics sometime, I have it in a 1U case with the GPUs sitting next to it on 50mm risers. It's quite ridiculous