As other have said, the multi-cal route leaves you usually with a can that suppresses one caliber pretty well and the others - not so much.I guess what I meant by multi cal. was I'd probably get one in .45 to use down to .22. Not so interested in shooting any of my rifles suppressed, although maybe that will change like you say!
22 is worth having its own can - as others have also said - 22LR ammo is dirty as hell so you need a can that you can take apart and clean yourself.
Aside from that, I know people that bought a can like an Obsidian 45, and that seemed to suppress 9mm pretty well. Remember, the native muzzle velocity of the 45 is way down at or below the speed of sound already and subsonic ammo options for 9mm are everywhere.
As I joked upthread, when you go for the beefier calibers like 10mm, all a can will do there is reduce muzzle signature, unless you can find a cheap supply of subsonic ammo for them, and I've no idea why anyone might want to down-shift a 180- or 200-gr round down to below 1000 ft/sec.
Don't discount a can on your rifles either. Particularly shooting suppressed 22LR - it's just about the most fun you can have and still have your clothes on with a host like a Ruger 10/22 or some other l'il rifle.