This is one area the USA is way behind a lot of the world. Suppressors are now mainstream for rifles, but you still have to pay the government extortion and a long waiting period so they aren't super common outside of the "gun guy" community. Suppressors in the USA are mostly screw on rifle and pistol cans. There is only one single shotgun suppressor from SilencerCo. It's not bad, but it's still a big muffler on the end of your shotgun. Plus it can only attach by using the correct choke tube thread adapter. It isn't the end of the world but now you #1 need a barrel threaded for choke tubes (which admittedly most people do), and #2 you have to buy their adapters for different chokes. They do not offer a turkey choke, and they also have some warnings against steel shot in some of them.
I hope I don't hate myself too much for saying this, but this is where Europe has it more figured out than we do with shrouded shotgun barrels. It's already easy to buy shotgun barrels, almost all single barrel guns (pumps, semi-auto, single shot, etc.) have interchangeable barrel. For example Remington could sell the heck out of a shrouded 870 barrel here, yet nothing is on the market, and I don't know any gunsmith who does such a thing. Of course with unlimited money, the sky is the limit.
As for subsonic ammo sucking in killing power, you are dead wrong. If you are interested in learning how to make it work I can go into detail as I have done a lot of testing in this area. I'll just leave this comparison calculated by KYP ballistics. These loads are near equivalents, yet one is subsonic, recoil is about the same, actually a bit less for the subsonic.
1 1/8 oz #6 lead at 1250 fps- 253 pellets - 1.55" calc. gel penetration at 40 yards
1 3/8 oz #5 lead at 1050 fps - 239 pellets - 1.63" calc. gel penetration at 40 yards.