Well, after months of reading articles and trolling the forums, I'm about ready to start construction of my home studio. I have a few questions (mostly related to budget). I'd like to detail what I'm considering doing here in hopes that someone will stop me if I'm making a mistake.

Keep in mind that the primary focus at this time is to allow me to play my guitar amp at night without bothering the family (our bedroom is above the studio). I have no plans to have a full band or even a drummer in there. I use Sonar and various synths (and I play computer games), but the amp will be the loadest thing in the studio. (an 18w Dr. Z Maz 18 if anyone is interested).
1. The room is approximately 11.5' x 11.5'. Building a room within a room is not an option.
2. Two of the walls are outside walls. One is block and the other is framed. Changing the outside of the other two walls is not an option (they are in finished rooms).
3. I plan to start by ripping out the existing drywall within the room.
4. For the walls, I intend to use a silicon caulk to caulk around the studs against the drywall that exists on the outside of the studs.
5. I plan to cut sheets of drywall to fit between the studs, and glue these to the existing drywall to add mass to the outside walls.
6. I next plan to put R11 between the studs (Auralex mineral fiber was considered, but too expensive for the budget).
7. *** I'm considering adding some random;y spaced blocking between the studs using 2x4s tipped upwards. Will this help?
8. Next comes resilient channels.
9. *** Next comes 1/5" drywall. I considered 5/8", but it is considerably more expensive that 1/2" at the moment. Does this matter? All of the seems will be glued together using a flexible glue.
10. Next comes another layer of 1/2" drywall, placing the seems in the opposite direction of the first layer. Again, all seems will be glued to make it as air-tight as possible. This layer will be finished.
11. The two doors will be swapped for solid-coor doors if necessary, but we're going to try and fill them with expandable foam and build a layer of MDF on one side. All appropriate gaps around doors and the window will be filled with expandable foam.
For the ceiling...
1. Glue/caulk all joists where they meet the sub-floor.
2. Glue 2 layers of 1/2" drywall up against the sub-floor. I'll probably be using 1x2 supports.
3. Add randomly spaced blocking of 2x4s between the joists.
4. Fill the cavity about half full with R11.
5. Next comes flexible channels.
6. Then a sheet of 1/2" drywall (all seems glued).
7. Then another sheet of 1/2" drywall (all seems glued).
We've also got one vent to consider in the ceiling, but I've got some ideas on that (love to hear any you have as well!).
I originally considered using Auralex Sheetblock between the two layers of drywall on both the walls and the ceiling, but that hurts the budget.

Without the Sheetblock, it looks like we can do this for $5,000. (this includes quite a bit lighting and electrical work)
Any input or guidance you could provide would be most appreciated,