that amplifier should do good on 2 BTL's, one of friend from CA uses 2 of the Memphis MC1.4000 running 4 of the BTL 18" compete around the world hitting over 170 DB. LOL!!!! pretty slick. 18 inch just have more corn area then the 15 inch, if your scared the amplifier is going to shut down go with the Memphis, I had friend using it and is legit, but I don't think that rockford fosgate 40001 will shut down, because the power handling, all that is a very nice amplifier that's for sure.