[...]- about downclocking the memory - mine are at 450MHz, but that's only because at lower MHz sometimes the driver crashes and also it seems to affect the hashing speed. [...]
Hashing with 7970, cgminer + MSI Afterburner I undercloked memory to the amount of 50-100 Mhz with core clock around 1140. I didn't see the impact on hashing power or driver crushes but GPU's fans speed and tempratures.