I'm going to make a very left field suggestion - buy bigger speakers with bigger drive units. It sounds daft, but I went from multi-driver ported floorstanders (3 x 4") to 12" tannoys and I went from regular knocking from next door (my speakers are on the outside wall 25' from the party wall on solid concrete floor!) to nothing with the Tannoys and I dont play them quietly. Bassy small speakers 'thump' - they have to move a long way, very fast to shift air for decent bass. Bigger drivers don't thump the same way for me. So there you go - buy some dirty great speakers is my advice