Do You Want A Sealed Unit Or One That Can Be Disassembled?
Gemtech Quantum built on a 10/22 or 10/77 barrel for the sealed system. John Norrell for an internal that can be disassembled. The above 2 are probably at the top of the Quiet List.
I would not regard some of the better Screw On Suppressors as Pop Cans when you are talking about overall suppression. Tom Bowers of www.subguns.com makes a very nice .22 Screw On Suppressor and is a very good bargin for the money. You can go to the home page there and look at some of Tom's products first hand.
The Norrell 18" integrally suppressed 10/22 barrel is the "Mac Daddy" of 10/22 suppressors for easy disassembly. I have one on an original Norrell/Ruger 10/22 suppressed select fire smg and it is tops. This suppressor can with stand 7-8,000 rounds of dirty .22lr before dissassembly and cleaning per John Norrell. He sells a spanner wrench and threaded dissassembly tool with his suppressors that make taking them apart a snap - and I don't mean the kind of 'snap' that makes you go, "Oh, sh*t!".
I have a couple of shooting partner's with a GT Quantum and an AWC. We have shot all of these suppressors side-by-side at the range to compare ............. that is really the only true test of the sound suppression and 'tone' and 'signature' of a suppressor.
Also have a Ruger MKI pistol with an integral suppressor by Ralph Smith of Red Dog Target Supply http://www.rdts.com/ in Arizona. Great work, very quiet suppressor, and a nice suppressor for the money. He also builds integrally suppressed 10/22 and 77/22 barrels for a very reasonable price.
Mark Serbu builds some of the best and quietest 10/22 integrally suppressed units and is priced reasonably also. I have shot a few of his suppressed 10/22's and Ruger MKII pistols - very quiet and impressive. http://www.serbu.com/1022.htm
In my opinion, I would stay away from Sound Technology/Mark White. While he is a nice guy, his suppressors have a different poi at different distances. Been there, done that, sold 'em.
That seems to be a mark of quality with 10/22, 77/22, and the MKII integral suppressors and screw on suppressors. The better ones don't change poi when shooting at different distances.
There are literally hundreds of c2 suppressor manufacturers out there and you're best bet is to shoot the model/brand you are most interested in and several more before buying to determine the best value for your money.
Good luck in your choice and a quiet 10/22'n to ya,
Pic is the SWR 77/22 'carbine' rifle. Very quiet unit with a 16" integrally suppressed barrel in brushed stainless.