I'm not sure. Maybe just call him down... flop comes ace high and he calls, after calling your pre-flop raise. What's he got here? AJ, AK, AQ, AT, what? Pretty sure he has an ace, and the other two cards out there are a king and a jack - the likelihood that he has your two pair beat is decent. If not he's probably got top pair with a 6 or 7 out draw (for the straight, or to move ahead of your two pair). I'd want to see a showdown, but the cheapest possible showdown.