Oh wow, this thread only has seven pages? And I thought the Denon 9200 was underrepresented.
I've been messing with the TH-909 for a while now trying to find the best pairing. It's super finicky due to the low impedance, but wow, they truly sang once a right pairing was found! Of course, this is subjective based on my ears, so YMMV.
They didn't like my DAPs much, such as the iBasso DX300, Cayin N6ii (a01) and A&K Kann Cube.
Similarly, the sound was average with my other DAC/AMPs such as the Romi Audio BX-2 Plus, ifi hip-dac and the Fiio Btr5.
My PS5 Soundblaster G6 sounded above average with these which was surprising to say the least!
Edit: Just discovered I hadn't set this into Direct Mode! What a surprise, it even got better! Seriously check it out.
A notch above came the iFi Micro BL, the highs were tamed and the low-end rumbled nicely.
Finally, I plugged them into my Chord Hugo TT2 + M-Scaler stack and wow, thumping low-end, clear mids, and highs that teeter on the precipise of bringing out details without sounding sibilant or noisy. Such an enjoyable and energetic listen!
Of course, badly recorded tracks will still sound bad, but I've used Tidal, Spotify and my own FLAC files and I'm positive to say that these are very amp dependant but sound so deliciously good if you could find a good pairing for them.