15' x 19' isn't all that big of a room...I think you could get away with the M22ti's just fine, depending on how far away from them you'll be sitting. If you're no further away than 10'+ I say go for it. If you'll be sitting much further back, then the M60ti's will work really, really well also.
Regarding the rear channels...someone around here made an excellent point (can't remember which one of you it was) that if you're rear channels are going to be on the wall just behind the seating area (like only 1'-2' away) you'll be much better off with another set of QS series surrounds in the rear. But if you've got some space behind you (at least 4'+) then the direct radiating M2i's are probably a better bet for those f/x channels.
In either case the QS series should be used for your surrounds...they're amazing.
It'll come as no surprise for the regulars around here, but I whole heartedly support your choice of Hsu for the sub. That room can be filled by the VTF/STF-2, but you'd really enjoy the VTF-3 a bit more. You've got a good amount of air to move around.
Good luck!
