I just had my basement redone and built a new HT room. Basically, the contractor installed R-19 installation within the new four walls. He then added high density fiberglass (Johns Manville, I believe) in the ceiling joists. I am pretty happy with the result - only low bass escapes through the ceiling, which was expected. My drop ceiling is lined with regular ceiling tiles.
I would definately put as much fiberglass in the back wall as possible. From talking with experts, leaving just one wall untreated negates the effect on the other treated walls. Since you cannot cover the entire wall, I would not spend the extra money on the QR drywall because sound can still escape through the untreated parts of the back wall. My contractor also recommended ceiling tiles over drywall ceilings if your waterpipes run through the basement ceiling.
