Intel Core i5 3570k
CM Hyper 212 evo
Arctic Cooling MX-4 paste
Corsair Vengeance 8GB 1600mhz
Gigabyte Z77 UD5H
Nvidia geforce GTX 480
Antec 1100 with stock fans
In a 27 C room, temps fluctuate around 32C according to the BIOS monitor.
After 30 minutes of prime95 using Hardware Monitor to check temps, max temp for package was 70C and average was probably 65C. Temps for individual cores were a little lower.
Did you remount the HSF and use the correct amount of TIM?
Your CPU has a 77 TDP, which is low wattage. So, if you were running stock clocks on everything, SpeedStep on, and turbo boost, you should idle about 1-3C over ambient/room temp. And my guess would be high 50s running the Prime95 Blend tests.
Is there a way to mount one or two fans in the front panel? There usually is, in Antec cases, and I'd recommend at least one.
Download Realtemp, IMHO, its better at monitoring temps.