Did you manage to sample the D 3020? I ask because I bought the Teac AI-301DA-X as an upgrade from the D 7050 I had which was starting to get problematic only to be dissatisfied with the sound quality., so interested to hear the thoughts on the a-h01.
I just found the way the highs and mids were presented felt restricted and "digitised" compared to how NAD presents the exact same music/voices which is very warm feeling and natural. Hell given the price of the AI-301DA-X at the time, I'd have rated the D 3020 even higher than it as I had the 3020 v1 back in the day. You get a lot of power and sound quality for the money with the NADs this much I can vouch for!
The Teac build quality and style though is superior to the all plastic NAD D series, but hey ho!
You also want to demo speakers in your listening environment as room acoustics in a store won't be the same as what you have at hone! Hence the recent foray into trying out potential upgrades from my Q300 but going back to the Q300 each time. As such I am keeping the Q300, even with the minor driver cone indents.
I've only compared the D3020v1 indirectly against the A-H01, when I was auditioning, I compared both using the sale DALI speakers and the Marantz PM6005.
The A-H01 sounded identical to the Marantz (unless on a big set of high power floor standers), spookily so.. the real seller for me was the separation and imaging, just like the PM6005 it just seems to be so articulate with a lot of music types whilst having that musical warmer/richer midrange on top
The D-3020 v1 I felt sounded close to the Marantz, but not quite as warm in the lower mid-range, just a touch, and the separation and imaging did not stand out either, it felt a notch down in terms of audio quality.
The D-3020 v1 was usually preferred in reviews but from all that I've read more down to the 'features' it offered over the A-H01 which doesn't have blue tooth etc..
The AI-301DA-X I would imagine sounds completely different just because it was billed as 'Tuned in Europe'!
As for demo'ing speakers, absolutely, your room acoustics would massively differ, although if listening near-field on a desk, if the speakers are relatively free either side, I don't think the room acoustics play as significant a part. And this may explain your Q300 experience, but I demo'd and have since demo'd a few speakers, and not many work 'near field' that well, Your setup looks wider than my own but it's still on the cusp of still being near field, it would not surprise me that the Q300 might be one of those (like the DALI) that just gel in near field.
Still baffling to me that almost a decade on and NAD still has the best small form factor speaker amp for desktop usage. You'd think someone would have tried to take a slice off of that already...
Hell, ASR even measured the D3045 recently and were actually happy to recommend it - not outstanding in any one area, but it did very well in every area (including the headphone output, which is normally an afterthought on non-dedicated HP amps) enough for it to pass comfortably.
Their earlier attempts like the D7050 measured like crap, but seems they've cleared this up.
I don't think there is a large market for desktop amps at all, and glad NAD have stuck with it, I'd get the D3045 if my Teac blew up..