I hope this will help drive home the advantage of an after market heatsink and fan. I have a 955, not a 940, but this should still help. I am overclocked to 4.1GHz, 1.404v and I have my NB at 2800MHz and 1.2v. The screen shot below shows my system under load after 15 hours of a blend test. I have a Cooler Master Hyper 212+ with an additional pull fan of the same type as the push fan. I picked it all up for $40. Anyway, my temps are low. My ambient temps in my case are about the same as yours. I think that you could easily hit 3.8GHz with 1.4v on the core and be at these same temps.
The stock Heatsink is terrible on the 940.
EDIT: Your ambient temp is a bit higher than mine, but you should still be well below 62C on the CPU with the Hyper 212 cooler. You should try to stay below 55C.