I shot the Silencerco Salvo 12 yesterday. We had it mounted on a vent rib Rem870 because that's what we had readily available that was threaded for chokes and took the included adapter.

You do not need sights that are very tall to clear the Salvo 12......the top of the bead on the vent rib was right about at the top edge of the suppressor. The factory Remington rifled sights would clear it easily, as well as any ghost ring sights I have ever seen or used.Basically, anything much taller than a bead on a post or vent rib will be tall enough.

It was much quieter........definitely still a shotgun discharge, but comfortable to do without ear protection.

I was at a demo day recently where there were lots of IWI Tavors, SBR ARs, a Nagev belt fed, and lots of other fun toys.  I found the 10" 870 with the 8" Salvo to be my favorite.  With the short barrel an mid length salvo setup at 8" it was still not hearing safe according to the Silencerco Rep.  We discussed the possibility of subsonic buckshot and slugs.  Some reduced recoil buck is already close to subsonic so it wouldn't loose much by taking a little off to bring it under.  It would certainly be cool to have a 14" pump with a 6" salvo that's hearing safe.

10"? Did it only hold 3 rounds

Yes and had a shorter forend.  I would much rather have a 14" with a +1.

We shot it out of a full-length 870. Of course, an SBS would be quite a bit louder.

I got to put a mag through a 26" 870 with a 12" Salvo shooting standard dove loads. Thing was pretty damn quiet. It seemed like the sound of the bb's hitting the trees were as loud as the shot.