Some tower heatsinks (such as that Xigmatek) are designed to redirect airflow down toward the components around the CPU socket. I don't know how effective this is, though. My Arctic Cooling Freezer 64 uses this design, and it doesn't seem to do much to cool the MOSFETs. Then again, I keep RPM on the fan very low to cut down on noise. With a higher RPM 120mm fan, the Xigmatech would probably be more effective at cooling these components.
If you're still worried about VRM temps, you can get small, stick-on heatsinks for them. Thermalright also offers a selection of more substantial heatpipe coolers.