I think it makes a huge difference to get those last notes about of the music, my wife says that she was surprised how much the subs helped. . . I have 20.1s and Kinergetic SW-800s amplified by a Pass x250 up front. I also have two super fast SVS-16 Ultras that work with my mini DSP/to do room correction and address those standing waves many people have mentioned. I make measurements with an Earthworks mic and REW and Multi Sub Organizer crunches the numbers that I enter into the DSP. I have 8 channels of DSP for my 2 Channel set up. I can't speak to doing this with less money or lower quality components. I believe you should match any sub augmentation with stuff of similar quality to the main speakers. With Maggie's they need to be non ported subs in my opinion to have more control and keep up with the panel speed. The coherence and imaging of my system is right on. I had some engineer friends over from work to assist me in installing my projector screen and they said that my neighbors should hate me. I told them I've never had one complaint. I turned the music up and they listened with mouths open. There was no boom just accurate involving full sound with pin point imaging. I took a long path to get here. I wish you luck on your quest ;)
-Steve
-Steve