The OpenPro/Ultegra's are always a great option, and are in fact what I ride on for most of my singletrack/fireroad excursions. A lot of times though, I find myself wishing for something a little wider to give the tire a rounder, fatter profile, something like the Salsa Delgado Cross, Sun CR18 or WTB Dual Duty. The downside of course, is that the brakes have to be readjusted for the new rim width compared to the stock rims.