Buy a bag of child proof outlet plugs roughly $5 for a big bag. Plug every unused outlet opening through out the house, not just your sound room. This prevents EMI, RFI from entering the electrical system, the reduction in back round noise is anything but subtle. One more cheap but highly effective tweak suspend all cabling with fish line from the ceiling, most effective in minimizing cable vibration, cable risers do not even come close in performance!
