This new class D stuff is pretty much going to obsolete the class A/B amps going forward. Close to 90% efficiency vs. 50% means less power draw and longer battery life in addition to smaller footprint and virtually no heat. Wetsounds, exile, and others are all moving this direction because of advantages stated above. Class D used to get a bad rap that the sound wasn't warm but the new Phillips chip everyone is using put an end to that.
I have a great arc audio amp for the in cabin speakers and 2nd sub which is class A/B but huge compared to the polk amp I bought to eventually replace it with the Polk D5000.5 I just bought
Wet Sounds, Kicker, ARC, JL, Powerbass, RE Audio, Alpine, PPi, Polk, and others moved that direction a few years ago, actually. Ive heard rumors of a class-D full-range from Exile, but havent seen anything yet.