much thanks for the suggestions and the link, this is giving me alot of ideas.. I may just shift the vent upwards so I dont have to cut through the studs.
Re: able dogs post - that sounds super effective.. are you saying I would make a whole another frame with 1x2s to attach the drywall to? that may be above my time commitment for this... but worth thinking about if it will be better in the long run.
The 1x2 PT is only to provide bearing for the additional studs that are place in the midpoint between the existing stud picture
Normally that type of staggered wall has 2x6 top and bottom plates. Since you only have a 2x4 plate you need 2 inches to equal a 2x6 (5-1/2 In.) so a 1X2 (1-1/2 in.) spaced a 1/2 in. from the 2x4 plate gives you 5-1/2 in. I know from experience that that is very effective sound proofing.
You never answered my question as to the need for that vent. It would probably negate the value of the wall sound proofing.
When I went back and looked at that vent which seems to do nothing I noticed you do have 2X6 plates, you merely need to add studs at the midpoint of the existing stud spacing.