I have the Coolermaster 532, same internals as the Centurion. Basically its the case that is the problem.
I have used an E6600 with and Abit AW9D Max in a LianLi case and get system temps of around 30 deg c. CPU was around 32 this is with an AC 7 Pro.
Put it in the 532 and temps shot up cpu is now 39 and system at 44. Used same cooler AC 7 Pro, so the only diff is the case. It previously had a E6300 and I was getting the same temps around 38 - 39 deg. Tried the E6300 in the lianLi just to satisfy my curiosity and temps dropped to 29 at stock. All temps measured with uGuru so add another 7 deg for CoreTemp.
The stock cooler is also blowing down so some of that hot air is blowing into your case. I would try an AC Pro 7 to begin with and at least the warm air from the cooler will blow towards the rear of the case.
Other than that changing the case with decent cooling would help a huge amount if the temps are of that much concern, but as Acrobat has suggested altering PCProbes alarm level wil stop the siren.