how big a room has to be until its considered large? just tell me length and width, assume an avg 7 or 8 foot ceiling. i want to know because im looking for a qs4 or qs8 surround from axiom. i think the main difference between the two is that the qs8 is made to fill 'large' rooms. is there any sonic differences (aside from lower extension)? if i can get the away w/ the qs4 i can save a few $$ and put that money toward stands or a sub.