If no moisture problems go with wood or carpet are what ever you want. A sub floor would only be needed if your floor looks like the atlantic ocean. wood floors such as pergo have an foam underlayment for sound purposes. 90# felt will also help with noise of walking on wood on concrete and can be cut and spread around to handle any leveling problems on the floor. Also install a drain pan under the water heater if you are worried about it leaking. They make them for washing machines too. Good luck.