I did a 500E too last year! In my case I hid the sub under the mat...
Also, used PPI amps, and the 2 link together pretty cleanly. I wanted to leave some wiring exposed; it was a LOT of work! Needed a 100 amp circuit breaker to deal with this setup.
Though my sub's not likely not as good-sounding a solution as Daesun & Guido (but it is time-aligned & has active noise cancellation), but I've got 3 kids so can't give up the trunk space!
