Sure, give it a go and hear for yourself. I think the MHA100 will drive anything but not ideally. You can drive an HE1000 to loud volumes, for example, with a 100 ohm source but it wouldn't sound as dynamic and controlled as a 1 ohm source. Your frequency response with a 100 ohm source also won't be as flat and you will also likely notice higher distortion. Just to clarify, the McIntosh's autoformer is designed only for the headphone amp, not the speaker amp and McIntosh is very clear about this. As for the output impedance of the headphone amp of the MHA100, just check Mcintosh's website and you will see that depending on the autoformer setting, it is either 8-40 ohms, 40-150 ohms, or 150-600 ohms. As you have a DAVE, just check the user's manual and you will see its listed output impedance of 0.0055 ohms. Now try and find any other commercially available source with an output impedance that low. The only thing that will come close will be a good solid state speaker amp. As for the output impedance of the MHA100's speaker amp, McIntosh doesn't specify it but since most speaker loads are 8 ohms and you state this amp is stable down to 2 ohm loads, then you can guess it will be well below 1 ohm. As an example, the Moon 600i mentioned earlier has an output impedance of 0.03 ohms which in theory should drive a speaker load as low as 1 ohm. As for other headphones to try, in addition to the HE-1000, consider listening also to your HE-X (25 ohms) and the EnigmaAcoustics Dharma D1000 (26 ohms). You can compare the MHA100 against the DAVE but it won't be an apples to apples comparison because there will be other factors at play beside impedance. For a truer apples to apples comparison, listen to any of these headphones on the MHA100 but at different impedance settings using the autoformer (low, medium and high) and you should hear a fairly noticeable improvement as you go from the high setting to the low. I think the fact that McIntosh even has these different impedance settings should tell you that impedance matching is important. As for the idealized 8:1 ratio (damping factor = 8) between input impedance of a transducer and output impedance or a source, you probably understand this isn't a hard and fast rule and that some things can still sound decent at 4:1 or 2:1 or maybe even 1:1 but when you start comparing against something like 16:1, as an example, I'd be surprised if you didn't hear a cleaner, more effortless and controlled presentation with the higher ratio.