I'm listening to my AFC paired with DX220 AMP1. My expectations were very high but I couldn't find what I hoped for (so far).
+AFC is the most comfortable headphone I've ever worn
The sound is usually overly thin and bright. I am far from being a bass-head and I love treble sparkle but even for me AFC is overly sharp in negative way so far. The sound quality is weirdly inconsistent across different songs, a track sounds extremely good but the next track on the album sounds like unlistenable garbage. (the two tracks sound equally good on my other headphones)
AFC sounds good with instrumental tracks, but songs with multiple elements (synthesis, vocals, chorus, drums) often sound very congested. Belive me or not, some tracks sound better with my $350 bluetooth Sony XM3.
Many people including Dan suggested AMP8 module on DX220 to pair with AFC. I will purchase that and I guess it will improve the sound.
There are still many tools I can play with (EQ, damping pads, AMP8) . Let's see