Not super sure, but I'm guessing AT LEAST 12 but probably a few more than that.
My Phenom II X 6 at 3.85GHz can run 8 easily (while I still use the computer) and can probably do 10ish max. So you can use those stats to guess for yourself.
I think the best way to go (assuming money ain't a thang

) would be an i7 if you can afford, and then buy a cooler, and overclock it.