Most users I've talked to seem to agree that 2600K at stock is just as fast as 6-core AMD @ 4GHz. AMD's stuff is last-gen, 2600K is current, so compare is not exactly fair, anyway. SB is not the next-gen high-end performance platform, either.
As far as I remember, I simply set all 4 turbo ratios to 45, and then adjusted voltage accordingly. using TUrbo mode with all pwoer saving features enabled. If your CPU slows back down, and never reaches 45 if set at 45, perhaps a CMOS clear, or maybe reflash BIOS is needed.