The problem most sytems have is uncontrolled bass which screws up the rest of the sound. Mana stands seem to reduce bass issues of that type. When everything isn't being shaken to buggery, the bass does appear to go lower, and cleaner.

My room measures about 27 by 19 with a 13 foot ceiling. The speakers roll-off about 34Hz, but there is useful and easily audible output down to 25 Hz. This does me fine because I think I'd be pushing my luck with possible room effects at frequencies lower than that. I certainly don't want to risk screwing up the sound in search of the last five Hz.