I have a cluster of a couple of dozen PCs, the number varies depending on what ones have died and I haven't gotten around to fixing them yet. My thread count is about 120; I hope to double that by the end of the year. All are Windows 7 (I know nothing about Linux), which I have found works better that XP or 8 for mining. Some are x86 and some x64, a mix of xeon and intel q9550 processors.
Having no desire to manage a couple of dozen wallets, and not knowing how to have a cluster solo mine to a single wallet, I use beeeeer.org pool.