The AcousticResearch M200 is a bit of a mixed bag.
The consensus is that it is a bargain in terms of the sound quality it achieves, and hugely useful with regards to its Bluetooth functions.
It is known for being slow, and a little clunky; although firmware updates seemed to have improved usage such as file tags greater than 128 characters etc. (just read a lot and this is from the top of my head; a headfi post mentioned ALAC support came with the firmware update, so Drops present version should be good)
couple of useful things- reports of 400gb Sd cards working is true, although some users of lesser sizes were having issues and had to try a few Sd cards before the unit worked well.
that being said, tricks for usage included ‘much faster operation and performance reliability if tags were stripped from files/files were kept basic’.
most people with less issues reported their steps as formatting the Sd card in the unit (not sure about 400gb cards doing this), and to speed up file copy, putting the card back into a card reader to load it up with media.
so fat32, confirmed working with 400Gb cards, best to not use tags.
The music is where the focus has been paid, (budget spent) and many purchases couldn’t fault the audio, saying bargain and ‘brilliant’ (sound)!
The apt x HD receive, and being able to use the class A to drive any headphones was definitely a strong theme that many declared ‘makes it a great buy just having this feature’.
consensus for $100 it is exceptional sound quality, and the optional iems are matched for the electronics/great sound pairing.