1900 ft3 is what, maybe 13x16x9 ? That is definitely an "M22-sized room". You should think about M60s if you want to play movies "really loud", or if you want to play music "really loud" in stereo (rather than 5.1), or if you wanted to play all types of music without the sub, but otherwise (ie for all normal applications) m22s should be fine.
Would you be keeping the DefTech's as surrounds ?
Note that most of the Hsu subs are "MKII" these days, can you give us the rest of the model number ? Something like STF-2 Mk II or VTF-3 Mk II.
EDIT -- by "play really loud", I mean "you are one of those people who is likely to say "listen to THIS" and reach for the volume control. If you're one of those types, go for the M60s