If you're idling at 58 degrees Celsius I suspect the heatsink is not properly seated and/or you didn't use enough thermal paste (I made that mistake twice during my first real heatsink install).
However, you may want to look into a better cooling solution for your setup though. I currently use an Arctic Freezer (for AMD CPUs) and it's kinda a PoS. While it did remove the overheating issues my old heatsink had it most certainly is louder than my old heatsink and will still reach a prime95 peak of 75 degrees Celsius. I would honestly go with Cooler Master's Hyper212 EVO. After installing it in a friend's PC and seeing the benefits (whisper quiet, Prime95 Stress Test peak of 50 degrees Celsius), I would honestly go for that.