Well i have the standard CPU cooler and have one fan in the back of the box.... there is a air vent on the side of the box but otherwise i do no other cooling..... the CPU Fan has a good heatsink on it.... i'm using core temp and it say 20C at the moment. PC Wizard says 28C (but this is the average)... and i think when i looked at the BIOS it was the same as the Core Temp.....
20C is close to impossible as that would imply that you ambient temperature would be >20C by quite alot