I really like riding my 'cross bike offroad. It is a blast, and I can ride virtually everything I can on the MTB. Just make sure to get you gearing right. You definitely don't want too much gear. Mine is geared, and I end up running in the 36/22 to 36/16 range most of the time when out on the trail.
I also have a Winwood carbon fork on mine, and it has held up to this abuse for close to 2 years now. It does have an alloy steerer, though. Your bike shouldn't break. Another tip is to get the biggest tires you can fit, maybe some 700x40 or so.
Why not ride the Cross Check for awhile and see if you like it? If it doesn't cut it, get a 1x1. i found my hands tend to get beat up running the 'cross bike offroad. I am also faster on the MTB since you are traction limited by the skinny cross tires.