I've been using M3 for more than a month and mainly listen to 16/24bit FLAC files at 44.1/48k. Performance is quite good and can drive full size headphones easily. But, please be careful when choosing MicroSD card ... Fiio support has told me that they have tested with Sandisk & Kingston brands up to Class 10 - I'm encountering frequent interruptions/buffering issue while using Strontium Nitro Class 10 (85MB/s). I think M3 plays well with Class 10 MSD cards upto 48MB/s speed as the problem went away once I switched to Sandisk MSD 64GB Class 10 rated at 48MB/s!
I think you will be very pleased with the M3, I've been in mine for the last 2 hours and detail retrieval is amazing to me for a <$75 rig! Running it into ED9's with brass filter:wink_face: