I'm sure if I buy another Rockford Fosgate 400A4 (assuming I can find one) it will be a good amp. If I can't find a 400A4 at a good price, do you think my MTX Thunder404 really puts out any less power than the Hifonics Txi 4408 or MB Quart DSC450? The Rockford, MTX and Hifonics all have 50-amp...