I ordered some live rock from KP Aquatics. I got the starter rock, not as much life on it. 15lbs was $160 shipped over night. There was a brittle star that perished and something else that ended up as a blob on one of the rocks. Survivors included feather dusters, a couple of snails, spaghetti worms, really cool tunicate, and of course some bristle worms.
The rock we use is an extremely porous type of limestone called “Miami Oolite”.