So I've got the AMD 965BE up and running at 3.9Ghz w/o issue with stock voltage and cooler in this case. It is LOUD though. I'd like to upgrade the CPU heatsink/fan. This case will do up to 163cm heatsinks. On air cooling, (up to $75 is not an issue), what is the best air cooler I can run in this case to hit 4Ghz or higher? I'd like that speed, but I'd take the current speed if significantly quieter.