If the acoustic wave hits the back of the studs then the timber will transmit the wave to the back of the plasterboard and hence to your ears, sound blocker is definately an improvement over conventional, if fitting a seperate stud frame to carry the board then it would be an idea to stand it out from the wall and fix the timber frame through the top plate to the ceiling, the sole plate to the floor and the sides to your internal return walls, before doing this glue a strip of sound deadening rubber along the top of the top plate and the sides and do the same at the bottom of the sole plate if it's being fixed to a wooden floor, if it's fixed to concrete/solid floor then no need for the bottom strip, they used to do a rubber backed sound deadening felt that was very good, something like that or similar glued to cover the party wall.
Infill between the studs with insulation don't use foam slabs there acoustic attenuation is not very good, use an acoustic wool or failing that rockwool or similar.
Doing all this will knock 4" or so off the room if using 2"x2" framing, to minimise deflection on the lightweight frame fix a wooden block half way up each or every other stud between the back of the stud and the acoustic mat that will be glued to the party wall. To skin it I would use two layers of sound blocker, lay the back course horizontal and run some silicon to fill all gaps make sure the plasterboard screws don't protrude you want the heads about a mm or so beneath the face of the board then do the facing boards vertically, tape, fill and sand or skim as prefered. I used this method on my place it works very well.
Hope this helps.
Lozzer.