I have a sak on my CZ semi auto, it's pretty much silent, the action makes the most noise when it cycles. It's quieter than my air rifle!
I did have the sak fitted on my hmr but have upgraded to a dm80, that's noticeably quieter than the sak on the hmr, can't test it on the .22 as its .17 specific.
I think on a .22 with subs for the money you can't beat the sak or Parker hale anything else just isn't worth it for the difference they make.