I have both, and like the original better. The channel matching is .1db or less so it's not an issue. They're very close in terms of sound, but the dot matrix display, remote which I never need, and controls via jog wheel is mainly why I like the original. Simple, just pop a Topping D10b on top of the original A90 and you're end game without MQA, bluetooth, remote controls, or needing to read a manual. I also have an A70Pro and with the menus at least it's more straightforward to navigate than the A90D. Sit the A70Pro on top of a 5 volt DAC like the SMSL DL200 and you'll never upgrade again... I put a D70Pro Octo stack together, but it makes little difference, both have the same size form factor, so it fits.