I've quietened a few, and didn't have to go to extremes.
I agree "quiet" is subjective...I shoot primarily longbows and selfbows, so I think I have an idea of "quiet".
The solution I've found is simple. Do the obvious tuning. The best string I've used on one is a 12 strand Dynaflight '97 with the loops padded to 18 with dacron. Pretty simple, and the difference was amazing.
Add a set of cat whiskers, tune them (you can tune the silencers like anything else, by moving them up or down the string), and the bow should easily be hunting quiet. Not longbow or selfbow quiet, but much quieter--no hoops to jump through.
One other thing that some folks don't think about is nock fit. A tight nock can be noisy--very noisy in some cases.
Chad