Personally, (my affiliation with iFi aside) I would choose the phone x Signature combo any day. Phones are so much more reliable and the Signature matches or beats out the sound quality of the DX300.
I'm a person that strives for practicality and flexibility when comes to driving a wide variety of headphones and IEMs, and that's why the Signature is my go-to (and I would have it even if I was not with iFi)!
Same here ... A good smartphone, compared to a good DAC/amp is so much better than a DAP with outdated hardware for 1000+ EUR. You have your smartphone with you anyway - every day, in every situation. And if you spend thousands of euros for audio equipment anyway, I am pretty sure that 95% of those people have a good smartphone anyway which does the job much better than a DAP. A DAP is just an additional device you have to charge, take with you, which needs updates and once it is "outdated", you have to sell it for a ridiculous fraction of the purchase price anyway.
I was absent for a couple of weeks ... therefore the question to you, @Sebastien Chiu and @iFi audio: do you have any information regarding the 4.4mm IEmatch?