You are running the signal through additional cables, connections, and, I suspect, a crossover in the Revel sub. A recipe for degradation of the sound. Does the Revel sub accept high level signal straight out of the monoblocks? If so, that would definitively (aka REL philosophy) be the way to go. If not, does the Bel Canto Pre have a second set of outputs to drive the sub? That way you are not messing with the signal that feeds the monoblocks.
Good Luck,
Arni
Good Luck,
Arni