I suggest you use the program K10Stat, PhenomMsrTweaker is similar but I found it caused boot problems.
Zip: K10Stat version .91
It lets you customize the cool'n'quiet settings, including the cpu frequencies, voltages, and northbridge voltages at all 4 power states. You can also set at what processor load percentages you want the cpu to change power states.
I currently have my 955 BE running at 800MHz idle at .875 volts, 26 C.
As soon as processor demand passes the desired %, it ramps up the clock multiplier and voltage. I have it set to clock up to 3.4GHz over 99% usage, at 1.26V, 49 C load.
Here is a good guide to setting up the program:K10Stat Guide
You can clock the bus way higher than 220, (I've seen people use 300MHz+) but don't bother, that's the beauty of an unlocked multiplier, you don't have to mess with memory dividers or anything. Everything I've read has said that you gain much more by overclocking the cpu-NB than you do the HT. I'm running my NB at 2.4GHz, +.1v. It made my memory settings much more stable and increased bandwidth.
Good luck and happy over/underclocking!