You can't go wrong with Rythmiks, either the 15"s or the 12"s, but you will definitely want the ported versions. I would not consider the 18"s from PSA. If you want an 18, get a real 18", and the most affordable decent 18"s at the moment are from Reaction Audio. I would also be looking at the 15"s from Reaction Audio and Hsu Research for the most bang for the buck.