Al, welcome. Any speaker can "fill" the room that it's playing in; the question is if you can have an adequately high sound level at your listening position. This can be roughly calculated using reasonable assumptions. Budget appears to be a major factor in your decision and at reasonable levels you should do well with M2s plus one of several fine subs in the $200-$300 range, such as the Hsu STF-1, Outlaw LFM-2 and XSub from AV123.

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Enjoy the music, not the equipment.