I had a friend that used the Mach 1's 15" woofers as a car sub, using the same size sealed enclosure as the original Mach 1's did. The woofers didn't have the X-max and made bad suspension noises at medium loud volumes. Looking at the 15inch woofers surrounds, it looks as if it can move 15 mm, it really closer to 5 mm.
I would look elsewhere if your planning to play low bass notes that require lots of cone movements.