From my testings, I found that the higher the NB clock frequency, the more performance up untill your NB is clocked higher than the cpu itself. At that point, the performance takes a real hit.

Thanks for the insights regarding the memory overclocking. It seems that we'd all be better off using low latencies rather than high frequencies, which is pretty much the same I noticed when comparing the AM2 platform to the AM3 platform. Highly overclocked DDR2 memory (620+) combined with tight timings (CL4-4-4) will be able to match any DDR3 configuration with timings equal to CL7-X-X and looser. This reminds me of the Msi P45 DDR3, which overclocked better at DDR2 timings!

Regarding the HT Link findings: are you sure nothing went wrong during the tests? I've done the EXACT same tests in combination with my 4870X2 card and an increase in HT Link frequency showed me a clear increase in 3D performance (3DM01 - Nature). This HT Link frequency has, in addition, given me fantastic performance increases when benching the HD3300 IGP at 1.1GHz.