I'm not familiar with overclocking the Phenom or AMD in general, but make sure that any existing bottlenecks or ... ratios if you will, are eliminated-
I'm running on an E6600 [Core 2] which by default is clocked at 2.4Ghz, effectively setting the memory to run at 266mhz [533/DDR].
If the memory is set to run at full bandwidth and the voltages [especially for the northbridge!] adjusted accordingly, the processor speed jumps to 3.6Ghz [50% over stock!], stable, on air cooling-- which needless to say makes a world of difference.
For a simple example:
SuperPi 1M @ 2.4: approx 22sec
SuperPi 1M @ 3.6: approx 14sec
Again, I don't know how much the AMD Phenom utilizes the full bandwidth of the memory right out of the gate; I would assume more than the E6600, but it's worth investigating.
FSB : DDR should be 1:1 if possible.