JL Audio XDM600/1 (D class, RMS 600 W x 2 Ohm) marine power amplifier (mono).

This potent monoblock amplifier employs our high-speed NexD™ switching design to achieve unprecedented efficiency and amazing power output from a very compact chassis.
Don't let its small size fool you, though... the XDM/600/1 generates serious subwoofer power, delivering a full 600 W of continuous power into a 2 ohm load (14.4V, 1% THD).
Designed for car or boat installations, the XDM600/1 is built with marine-grade materials and features an exclusive, dual-mode input filter for noise-free performance in boats or cars.
Automatic turn-on capability (via signal sensing or DC-offset sensing) is also onboard for easy factory system upgrades.
Targeted specifically for subwoofer applications, the XDM600/1 includes a variable slope low-pass filter with continuously variable cutoff frequency selection from 50-500 Hz. 
With the addition of an optional HD-RLC or MHD-RLC (water-resistant) remote level controller (each sold separately), the amplifier's level can be adjusted directly from the driver's seat or captain’s chair.