I personally don't have any advice off the top of my head for specific coolers. I do know that newegg.com, svc.com, etc. have some nice selections. It can't hurt to cool the southbridge. I plan on doing mine. My previous Epox 8rda+ Rev 2 had a Heatsink on the south bridge. The Southbridge tends to get pretty warm on the nForce 2 boards leading to sound distortion, skipping, etc. Good luck.
- ThePCGuy