Yeah, I think setting the fronts to small would probably help with bass response for two-channel playback.

Another question (possibly been asked before and dismissed for some reason I can't remember)... Have you tried a lower crossover for the center and surrounds? The Cinema i is rated to 80Hz and might perform well with a crossover of 100Hz (maybe even 80Hz), and the Monitor Audio Bronze surrounds can get down to 65Hz (which might work well with an 80Hz crossover).