With my Denon A1SE amp, and SVS PC Ultra sub, the recommended settings appear to be with the speakers set to 'small' on the amp, and the sub's crossover disabled. But it sounds better to me with the sub's crossover set at 80Hz and the speakers set to large. There seems to be less of a 'phase' issue with these settings. I think the Denon's crossover is mucking around with phase, whereas the sub appears not to affect it. So why should I disable the crossover on my sub? After all, isn't additional filtration at the crossover frequencies a good thing?