I am also running the Sabertooth X58 and i7 950, so far im at 3.8 Ghz with idle temps at the high 30's low 40's... I am using the Corsair H50 liquid cpu cooler, and I really have no idea what I am doing.
everything seems stable and the stress tests pass fine. haven't tried 4.0Ghz yet tho.
Please give me some details! I have the exact build as yours, I only want a small OC like you stated. If you wouldn't mind giving the details of what you selected, it would be highly appreciated!