Horizon divers let's you dive to your certification level: I'm solo certified and they let me dive the S. Grove with no hassle. It's been a year since I've been out with Silent World, but the last time I was, they were also accommodating and allowed me to dive the Spiegle Grove solo. In both cases, you'll need to hire a guide, not many operators provide free guides in the Keys.
I also like and mostly dive with Conch Republic when I'm in thbe upper Keys. They have a a big Newton 46 boat which will be nice if the December marine conditions are poor, which can be the case. They're not quite as accommodating on the whole solo diver thing but are very oriented to experienced divers: including tech divers and folks on rebreathers. Again, you'd need to hire a guide if you want one. I really like the people at this shop.
There are a lot of other good shops too, but I tired to focus my comments on the ones that go to the wrecks frequently and are good for experienced divers that need no or very little assistance.