Agreed about Zack being very helpful. If you look at their page they pretty much explain the difference. The Keys has the typical purple/pinkish coraline on it as well as a good deal of life. The Gulf doesn't have the same type of coraline, but does have some, it does, however, have the most life. Coral rock is just Gulf rock, with all of the life associated therein, with corals already attatched as of harvesting. The live base rock is what's left in the bottom of their take and is basically 'left overs.' From what I understand, it doesn't have as much life or coraline, but still has the bacteria colonies.
I'm setting up my tank now and am, probably by the end of this week, going to order 40lbs of Key and 30lbs of coral. I like the colour of the keys, and the life of the Gulf, plus, as expensive as corals are, I'm hoping to make up the extra money for the coral rock by not having to buy as many since I'm already getting some. After I get everything I'll post a bunch of pics since I'll just be tickled pink. Or something.