I'd like to sound proof my basement as I live in a bungalow and the music is quite loud in the bedrooms above.

I'd like to listen all night and not disturb people upstairs. How can I do this?
Thanks for the encourgement Max.

Krell man how did you fix your air vent problem and what was the end result like when it was all finished?
Good place to start your search is here:
Hey man, I relate to you, I live beside a highway and it gets really loud especially at peak hours with the honking. Even at night, the engines from vehicles passing by is loud. My neighbours recommended this noise barrier wall for residential home, it worked great and I can catch good night's sleep, I'm sure it will help your case too.
Another important consideration is to make sure any air gaps are sealed with acoustic caulk when framing for example.  HVAC noise can be reduced by inserting a "box" in the line that is lined with 703 insulation.  These techniques and more worked when we were building my brother's recording studio.