I know you don't want water cooler, But how about the Corsair H100i? Gives you room to OC, the H80i isn't as good as the H100, but works in 90% of the cases where the H100 might be issue. Its a closed loop and should not ever leak. I had my Orignal H100 for 2 years so far, still keeps my x6 1100T at 4.1ghz under 60C. I also run the H50 in another AMD system and had that the day it came out, works like a champ.
Air cooling, I don't think your going to get any better then what you have, or well you can, but you'll still have clearance issues.