I realize this is an old post, but it's the sort of thing that bugs me so I want to answer it.
Audeze's "spec" of a minimum of 100mW is complete nonsense. 100mW would drive the MX4 to 125dB, and their "recommended" 250mW will drive them beyond 128dB. For reference, 120dB is the threshold of pain for most people and will cause permanent hearing damage in less than 10 seconds (about 8 seconds, if I remember).
78mW will also drive your headphones beyond 120dB.
I mean, 1mW will drive the MX4 to 105dB, which is more than twice as loud as what I consider "too loud" (and will damage your hearing in less than 5 minutes).
Anyway, in order to keep this on topic, Macs have sounded great for years. I have an M1 MacBook Pro and had a 2014 MacBook Air before that, and they both sound fabulous with any of my headphones, and get loud enough with 250ohm Beyers and 300ohm Sennheisers. Heck, my iPhone 12 mini also powers my headphones fine and sounds great doing it. I see very little reason to buy anything else unless I want a knob or some other features.