Rojo-sy (Redsy with Espanol twist-per some older thread),
I keep forgeting that you are a fellow Drummer-Sparky!
Have you considered muffling your Toms? Cymbals don't workout well being muffled, but their higher Hz sounds decay a lot more per distance, than the sound of kick drums, snare drums and toms.
One really good way to get a grip on sound proofing + room tuning is to check out some practice studios.
Rent a studio for a few hours, and either play alone or bring the whole band there for a jam. Also pay attention to others and just what sound passes into the corridors.
For me personally, to reduce the overall sound of the kit (being a 13 piece double kick set with rock style cymbals) I furred out from original walls - only out 2" total. No direct contact between existing walls and the steel studs.
Inserted thin insulation - the stuff used by HVAC installers to wrap their ducts at joints and such - and let it hang kind of loosely in the wall cavity.
Sealed around outlets and at floor/sheetrock joints with silicone sealant (flexible when dry).
Sealed up window mounting points (inside and out), plus replaced windows with double pane setups.
Added a 2x2 T-Bar grid, 6" below the existing hard lid. Inserted R-19 3.5" insulation bats in the ceiling space.
To help "Tune" the room better, one furred out section was "offset" by a small fraction, resulting in a non-equal room size.
This helps reduce the problems involved with crappy sound in a Rectangular Room (mentioned by a member). One wall was offset 2" more at an end.
If you can afford Neoprene, use it to gasket and seal stuff.
Having done some very simple stuff, had a friend play the kit "hard", while I observed from outside.
Sound intensity at 10 feet from the room was equal to normal conversation!
My Wife opened the door, and BOOM!!! Loud As Heck!!!
Good luck and have fun playing!
p.s. what kind of kit do you have?
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!