I've got one of the Randall ones. I don't use it much anymore because my Vetta doesn't need too much volume to sound good. I liked it a lot for tube amps though.
It does a pretty good job of quieting things down. It's not like a whisper quiet thing though. I could turn my 50 watt power amp to about 75% without it being to loud outside it. I did use it to record a lot and it was cool for late night jamming when the kids were in bed. I put it into a closet in the studio in the basement and it kept it super quiet.
The recorded tones sounded pretty good, there is a slight mid rangey hump in it but it could be dialed out pretty easy.
I might sell mine if you're interested. I just don't use mine that much anymore.