I really wanted to get a Fi BTL 18" subwoofer for use in a car and possibly other various occasions. But I took a trip over to Guitar Center and tested out the JBL MRX518S. I was amazed with its volume and clarity. I have never heard the BTL so im curious if it can get louder/sound better than the JBLs even if it is not in a car. If anyone knows anything that would be a great help. Thanks. Also I understand that they are not really similar speakers, and I plan on using it more when it is not in a vehicle.