As a 2 cents, from using an already present *outside office* at my house and turning it into a Studio with 2 rooms.
Resilient bars are good, even if just for decoupling. used in roof and walls to great effect.
Have you thought of floating the floor inside?
I have an outer wall with 2 inches of rockwool, resilient bars,2 layers of acoustic plasterboard with acoustic membrane between them, followed by a 2 inch + air gap all the way round (no parallel walls) floating inner room with acoustic plasterboard on outside, 2 inch's of rockwool followed by resilient bars, and another sandwich of acoustic plasterboard and membrane and found the results quite effective and did it all on budget of around £2800 or so.