Search the threads. There is a ton of info. I have a full basement that is Bar/TV (80"+58"). I have 4-18" subs and regular 5 channel surround. The simple answer is there is no way to soundproof your basement on the cheap. I used roxul in all the joists (many will feel this is unnecessary vs regular bat insulation), i enclosed all my pots in sealed mdf boxes, i tried to seal as many cracks as possible with sound caulk, On my ceiling and a few walls, i used soundproofing isolation clips and mounted double layer drywall with green glue in between. I filled all my gaps in the door jams with spray foam and used solid doors. I did not take the time or $ to go after the HVAC. The results have been good. The higher frequencies are extremely dampened. At 110-155DB, not a lot of the higher frequencies are at a level to be bothersome to anyone on the main floor. If you follow the HVAC runs, you can hear noise through them (at low levels though). The low frequencies, however, are still coming through a bit. I still haven't added any bass traps or properly treated the room, which i'm confident will help (somewhat). Sound is like water-it will find the path of least resistance and leak. If you're not a bass head and watch at sane levels, then i would think bat insulation, clips, double drywall and GG would suffice. Head over to the soundproofing company website for some great reading. They were also excellent to deal with.