Core 0 and core 1 shows 33 and 35 C in speedfan.
I also use the e6600 and the orignal cooler.
I reacently bought this comp, and this time I decided to listen to others advice about removing the original theremal grease, since it sucks big time, and put on a good one. Through my research I have found out that the best one is "Zalman Super Thermal Grease" - better than artic silver even. And this explains my low temperature.
Im currently runing both cores on 100% and I now have the same heat as u do! (51c). And hey, it's summertime too, even though it's not that hot today