You could possibly mount it under the front passenger seat. If it wouldn't fit there, then maybe inside the storage compartment in the rear. If both of those fail then you can always mount it on the rear of the back seats.
keep it as close up front as possible so you will have shorter runs of power wires and rca and easy adjustments, I would say under the pass or driver seat.
:iagree: No room under the dash for an amp plus that area should be kept clear of additional electronics. Just one more thing to disconnect if you need to get under there and I would be worried about interference. Mine is on the rear seat of the driver's side, but that wasn't my first choice.