Wow, I am sure glad I live in a house with thick block construction. I tested my system out by cranking it way louder than I could stand, turned on a bass heavy movie and walked outside. I walked five feet outside my door and you couldn't hear a thing.
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I am using an SVS NSD12/2 and two DefTech BP7001sc with built in subs using 1,500 watt amps in each tower. I figure if I ever have to move back into an apartment, I would never be able to use any of my gear to anything close to it's true potential.
BTW the Gramma will only decouple the sub from the floor which will help with bass transfer mainly thorugh the floor, as far as bass through walls, your gonna need some serious room acoustics or turn the gain down.