I am looking to purchase a single disc floor machine. Besides speed what else should I be looking for?

Marble honing and polishing can be very hard on a floor machine. For this reason I would purchase a commercial heavy duty machine. A heavy duty machine would be at least a 1 ½ horsepower motor . Stay away from the cheap 3/4 horse buffers. While these may work, you will burn them out very fast. Contact several of suppliers and ask to see the machine in operation. Also ask for references of individuals that have purchased these machines.

TIP Purchase a machine that has a solution tank. A solution tank is a water reservoir which fits to the handle of the machine. This will make life a lot easier. Solution tanks can also be purchased separately from janitorial supply houses.