Hi again—you came to this forum for advice. All forum members, so far are recommending you buy and use Class D amps. Engineering science and applications have moved forward onto Class D amps. Are you still wanting old used AB amps? Why?
If I would buy a new amplifier then a good class D is what I most likely would buy, and as
@everettT wrote low heat generation is important to me as well. Also note that an efficient power supply is very important as well as most of the time the amplifier will output low power (1-5 watt or so). I look at idle power as well as standby power as important factors when buying something as that is the state the device would be in most of the time.
That said, I'm only using an Denon AVR that has the amplification I need, but has class AB amps.
I do have two Genelec 2.1 setups that have internal class D amps. The alternative was active monitors from Neumann but they use class AB internal amps that uses much more power and produces much more heat. So, that was an important part of my reason to buy Genelec. The most important part of not buying Neumann a few years ago was that their room EQ and setup software was of flaky beta quality at that time, reading from posts on ASR.
Both Genelec and Neumann makes excellent active monitors.
