What is your ceiling going to be? If drop ceiling, not sure how much good the double drywall will be. Some people lay drywall on there drop ceiling tiles to stop rattling. Not sure I would go double drywall on poured concrete walls and other walls if ceiling is just drop tiles. If sound passes up through ceiling....
In mine, 2 walls face foundation, 1 wall basement, and another stairs/basement. I followed the advice of others, and did the floating ceiling, decoupled walls, and double drywall. I even built a second wall in front of my stair/entrance wall, for a totally decoupled room-in-a-room. I don't care if sound in the adjacent basement room is heard, as long as it stays in the basement, so did not double drywall other side.
Double drywall has it's problems, but is worth it. Watch out for outlet boxes, use box extenders if possible instead of blocking behind box (depends on if you go insulshield or not for absorbitive below ear level, 2 1/8" beyond box extender reach I believe). The floating ceiling joists with double drywall made can light insertion difficult as well.
If you need to isolate sound as much as possible, this is the best way. Acoustiblok may be better, but it aint cheap!