adding equipment (butt kickers) to a completed theater???

[avncars]

hello all! it has been 4 weeks since my little theater rooms completion, in that time i have watched every bit of 35 movies, probably more...i must say, i absolutely love it in every which way possible! i feel like i have left my house everytime i walk in and close the door. as much as i love the room, there are a few poor choices i made during the building process, mostly in equipment. first was one i already addressed on the forum, and thats the projector. but no big deal! i am ordering an up to date 1080p epson 8500 before the end of the week. second was my surround speakers, but now that they are calibrated they are far better. third, and this one kills me the most!!! i dont know why i didnt go with a 120" screen?! but its too late to change that now...now my question to anyone who has or knows about the "butt kickers"...how do they work? do they have to be put in during construction, or is it easy once every thing is finished off? i just think they would be a great addition, its not that i need more in the low range department at all. any help or info on the "butt kickers" would be awesome, thanks...