Quiesence is 6-pack only. No more than 6 divers on the boat. They do not put a dive master in the water as part of the price. Don't know about Silent World. Quiesence is my "go to" shop in Key Largo. Note this, because you asked for Key Largo and some other truly great shops, like Conch Republic, do not have comparable access to the sites in John Pennekamp park because the shops are farther south.
Quiesence has nice size boats. 30 foot newtons. A superb loading system where you sit on the transom with your feet on the dive platform, the capt lifts up your tank onto a ledge behind you, so you just slip in to your gear and step off. No getting up and down or shuffling around with fins on. Just the greatest! It is the total opposite of the cattle boat experience.
I forgot also, they have tremendous ladders, very wide, big diamater bars and rungs that are easy to grab and hold on to, rungs wrapped with rope for no friction. You go up, step on the platform, spin and sit on transom and unbuckle. Capt holds your gear off and by the time you slide out and step into the boat it is already racked up. They will switch you over also, and they know about bp/wings and how to switch them out. You can do your own gear if you want, just tell them.
However, if you want an in-water guide you will have to hire one, which you can do through them.