I am trying to avoid buying a Class D amp. They say good things come in small packages. Bleh.
First is the theory of operation. While it's actually a bit better than Class A/B amps, they create high frequency oscillations, and if they go haywire, they can fry speakers. It's basically 4 "matched" FETs working together in a push-pull configuration, at 100KHz or higher. Think of it as 4 people in a long canoe, each pair facing the other. The two at one end stroke their oars, and then the other two. That's how it moves the speaker cone in and out. Where it beats a Class A amp is you don't need a constant voltage on the output transistors, that only creates heat. It's so the transistors react faster if they didn't have voltage holding them up. Not that Class Ds run cooler, they're just more efficient. You also don't need a large transformer in the power supply, saving weight.
Another factor is impedance. You can't just connect cabinets unless you meet minimum impedance ratings, usually 4 ohms, or up to 8. Some run at 2 ohms, but it has to be 2 ohms, and only 2 ohms. And you can't let them overheat.
Now, in case you do have an issue and your amp smokes, a lot of places are unwilling to work on them. If they do, they'll just replace the module. Not cheap. The reason is almost everything in there is surface mount. I would imagine sooner or later they may start replacing parts at component level, but few do right now. If you could figure out which module is blown, power supply, preamp or power amp, you could swap the boards yourself and save the bench fees. If you need to get a repair, ask the shop if the work to the component level.
But what really got me is the "power ratings". 1,000 watts for $500. Wrong.
I used to work in a department store when I was in school, and we had these cheap stereos by SoundDesign and Audiovox. In big print they'd say 344 WATTS, and in the fine print it would say I.P.P.-Instantaneous peak power. Say there is a very loud bass bump or cymbal crash. For about 5 milliseconds the amp can reach 344 watts. The FTC stopped that and made audio manufacturers rate wattage in RMS, or continuous output.
This appears not to apply to Class D, for some reason, especially in instrument amps. Actual is more like 250-400W RMS, not bad, but you're not getting what you think you are.
End of rant. I'll be looking for an older Trace or SWR. I may get an inexpensive Class D just to try it out. I do have Class Ds in my cars and my home, but I do the one thing everyone should do when you buy a piece of equipment...Read The FUUUUUUUll Manual!