In my HT large sounds better than small. My Denon rolls off at 80 for small, and that is just too high and puts too much emphasis on the sub. So I can either pony up an buy a top end sub, or let the towers I already have make a seamless transition to the sub at about 40hz.

Panny 3000 PJ, 118" Carada, Denon 3300, PS3, Axiom QS8, PSB 5T, B&W sub, levitating speaker wire