For most of the DO ENT world, a good personality/good rotation/good work ethic can make up for a less than stellar boards score. Also, the base students can have a big leg up in my opinion as well--that is if they have a good personality, than it shows over a longer period of time, and assuming they have good stats, than it will be difficult to take that position away from them.
With all that said, I think the previous poster was right that a magic number of 600 is what you need.
One exception to all this is PCOM's program--they function more like an MD program (probably because they all are MDs except for the director). Scores and research matter more than other DO ENT programs, and they really like to see the USMLE--not an absolute requirement by any stretch, but if you have good USMLE scores and good COMLEX scores, than you will have a leg up on the guy who has just good COMLEX scores. I'm guessing this is probably the case at other places that have a lot of MDs on the interview panel. PCOM also likes research. PCOM has the best clinical exposure in my opinion of all the programs.