whoom instead of BOOM

hi everyone. new into home theater(though been running loudspeakers off a tv since the early 80's). anyway, i'm having a problem with the low frequencies. at the volume at which i get the spls i want(pants rattle a bit, couch vibrates etc.) i get a whooom response and not BOOM and lose definition and clarity. is it possible to acheive these spls without the "whoom" mucking it all up?
the room: 35x25x10 it is not closed in completely
the system: mirage m5si fronts, mirage 595si rears, mirage om-c2 center, mirage bps 150i sub(also working with dialing in a polk psw12 sub together), onyo txds797 processor. the front end is a panasonic dvd-s97.
THANKS!!