try Elemental Designs, maybe a nine.2 (400X1 RMS, but very conservative rating) My nine.1 is rated at 1200, but is closer to 1700 RMS) www.edesignaudio.com
I use three off their amps - 1 nine.1, and two nine.4's. Best amp out there for the price. I've used Zapco, Orion (old and new), and Soundstream class A for amps in my boats before, the ED's work just as well in a boat.
While I don't use them, their speakers are also very nice.
They also have the best warranty out there.