58C isn't in the dangerous range, it may shorten lifespan a little. I think if you were to get the case temp down that would solve help quite a bit.
My CPU tends to run 12-13 degrees higher than my case temp, but I also have a good heatsink and a 22 inch fan circulating the air. Right now it is 22C system and 35C CPU.
If you can get better airflow in your case, and it isn't in a closed space you should be able to drop temps a good 10C depending on your room (25-30 for room temp), but you really aren't too bad.