I assume you are doing the usual prime95 stability tests (there is little that more frustrating than a hangup 5 minutes from the end of an encode even more as you do it for a living).
Given the intensive nature of video I would not push it much above 3- 3.2 GHz on a stock cooler, that is likely to require a bump of 0.1V as well.
On a decent cooler (probably not air based, or if it is air cooling it will be very large and probably very expensive) and case layout I would probably drop the RAM timings a bit if you are running it linked (maybe set a few to 5 or even 6) I day say 3.5 GHz is not out of the question.
This being said overclocking should be definitely be done in baby steps when you get this "extreme".
