I looked in to the BMC Monster Cross frame as a possible Cross Check replacement for myself. In the largest 62cm, it's tubing has the same OD as my CC (28.6 top tube, 31.8 down tube), but thinner walls (0.8/0.5/0.8 vs. 0.9/0.6/0.9). I'm not sure what your Double Cross has, but I'd guess it's in this range--ie, if it's not stiff enough, the BMC won't be any better and might be flexier. I want a frame that's less stiff than my CC, so I'm still tossing around the idea of the BMC.

You could take a look at the Velo Orange Campeur. That would let you try low(ish) trail geometry while you're at it.