The article and drawings provide some good construction tips for sound reduction. The plywood is something I haven't seen used for something like this. The specialty drywall is really good stuff. I don't remember any pricing anymore, but I don't recall is costing so much more that would make it cost prohibitive. Mass loading, on the other hand, is really expensive!
Back in my college days I worked on the construction site of a 8 story condo building. My father was the developer and GC. He wanted to make sure the apartments were totally silent through the shared walls. Cork over concrete floors, two completely independent metal stud walls with 12" separation between the studs for a total depth of 21" including the double 1/2" drywall on both sides, and completely filled with pink fluffy fiberglass insulation. We would demonstrate the sound proof properties by having prospective buyer couples, one on each side of the wall, pound the wall and yell as loud as they wanted, but no sound was heard on the other side.
More recently I built some homes with theaters, some really nice, others were on a budget. It's better to stay away from using wood studs. For double walls like your drawing shows, use something like cork or rubber to separate the top and bottom plates from structure for the inner wall, double drywall with metal studs, first layer attached normally, the second is mostly secured using minimum screws and Green Glue, not cheap, doesn't go very far so lots of it. Double ceiling. Go nuts and build up the floor, cork is pretty typical. Depending on how much separation you can afford between the walls will determine what type of insulation you'll need if you're trying to hit a STC number. The more separation, the more common and cheaper the insulation can be.
Also, you'll need to consider building code. With electric outlets needing to be every 6', you won't want to cut holes in the walls so run the electric conduits on the surface and cover with crown moulding and decorative columns.
HVAC is a royal pain. It's a pipe to everywhere else in the house. Extra bends with dampening inside the ducts helps but sound will still be heard elsewhere if it's not a dedicated system. One cheap and dirty trick that works better than nothing is to use flexible ducting and add some bends. The bends add resistance to the system so more duct runs or larger size will keep the air flowing. Theaters tend to get hotter than other rooms so this is something you'll need to really be confident will work, but again, more holes means sound can escape.
Lights are another source for holes. Lighting can be surface mounted so the holes are at a minimum.
www.soundandvision.com
