I guess it really is a gamble with which CPU ya get. Its my first i7 though. Maybe I will try pushing with 21. being dead honest I can go quite far at 20. I can get the clock up past 220 I really love this X58A-UD5 rev.2. A real animal of a board. Couple fans on the NB, the 2 heatpipes going around the mosfets helps move the heat around well as well as the big SB heatsink near the bottom being part of the heatsink arrangement. Its one of a few of many boards I have owned in the past that I can really swear by so far.
My board gives up around the 210 mark, I've had it up to 220, but not stable.