Re: Old Victorian with no subflooring on upper floors
The 7/8" Drywall Furring Channel is explained in detail here: http://www.soundproofingcompany.com/...t_sound_clips/
That decouples the system, which is the first step. See the previously linked article for more detail on the rest of the assembly.
You would use standard insulation, as exotic insulations have no lab data that supports their use and expense.
You would use standard 5/8" drywall since it's $8 a sheet and wonderfully heavy. The specialty drywall you mentioned would be ligher and therefore less isolating.
Damp this 5/8" drywall yourself.
Your ceiling would require no more than $400 in specific soundproofing materials. He rest is standard insulation and standard drywall. Maybe $50 worth of the furring channel that you would get locally.
Keeping it Quiet