The amp modularity sold it on me. I also wanted a more holographic soundstage. I'm reading praises for both amp 8 and amp 9 (and even amp 7) - amp 9 makes me very curious since it apparently has a micro valve (tube) in it and I prefer valve amplification to solid state (actually, I prefer single ended triode valve amps lol to be more precise).
Watching a video comparing the M11 to the DX220, both were snappy enough for me - yes the Fiio unit is a faction snappier, but it's not the most important thing for me as a user and both are snappier than my now very old AK 120 II unit.
Also, same said video, I preferred the DX220 UI to the Fiio UI. I'm very fussy with UIs and very touchy with them. I don't like clutter and I like things k.i.s.s. Plus, larger icons and text on the DX220 are easier for my tired and poor old eyes (yes, eye problems too).
Interestingly, the weight on the DX220 is heavier (177gm vs 240gm from memory) - it's also slightly smaller, which I like too, since I am not a fan of massive phones in my pocket (I find them very annoying to be brutally honest).
I like the look of MangoOS so far - I'm still looking for a video that shows more in depth the MangOS.
edit:
As it stands, the DX200 unit sells for AUD $1399 here in Australia and it looks like I'm going to be lucky (first for me lol!!!) to score an ex-demo unit (complete with all box and accessories) from a retailer for AUD $950 - $400 AUD+ off the price...