Before getting married a couple of years ago, I could play my home theater audio as loud as I wanted....which really wasn't all that loud or so I thought.
Post marriage, I had to turn it down a lot. That's roughly $20K in audio equipment that's not getting used to its best.
So for the times when wife wants to go to bed early and I want to stay up I pull out a fairly good pair of headphones. I forget the brand name but they cost around $500. Granted it's not 7.1 surround, but it sure beats spending $50K building on or as in your case trying to figure out a way to do it on the cheap without having problems with the permits and such.
As a side benefit of these headphones, if you later loose interest you haven't spent a ton of money on something you can't use for anything else.
Samsung 64F8500, Panasonic 65VT50, Oppo 95, Tivo Roamio for OTA, Dish VIP722, Marantz AV8801 preamp, Rotel Amps, Atlantic Tech 8200 speakers, Seaton Submersive HP, Calman 5, Chromapure, Accupel DVG-5000, VideoForge HDMI II, i1Display3pro, i1pro2, eecolor colorbox.