Will M3K be upgrade over FiiO X1(1st.gen.)?
For me it was. The m3k is a good bit smaller, looks more sleek imo and is easier to use overall. Best of all, no awful mechanical scroll wheel, instead has touch capacitive buttons and a scroll bar. Which are quite responsive and snappy making navigating the ui(is also nice n simple) pleasent and easy to do.
I've only charged mine once the day i got it about a week ago and it says i have 4/5 battery bars left, after about 7 or 8 hours playback. My 1st gen x1 would already need a charge or be dead by now. Fiio claims 24 hours of continuous playback and 38 standby and i would say it's not an exaggeration at this point in my charge cycle.
Power wise, it's plenty strong enough to drive my fiio f5 iems and even my ath a900x's. Tho the a900x's require volume to be on the higher side for medium-ish volume but still does a great job without the need of an external amp.
Sound quality wise, compared to my x1, it's sounds... more refined? Just as good if not better at least to me. I don't have any fancy measuring devices to test my thoughts so i can't say for certain, but considering the price it is definitely good.
My only nit picks with the m3k are that it doesn't have a dedicated line out feature for external amps. I'm not sure if that could be added with a future update or not but it's not a deal breaker. I just connect my trusty e12a, max volume on m3k and all is well.
The scroll speed could use a boost, especially if you have a larger library. It works well enough but it could definitely benefit from some more speed. If fiio can release an update with added settings for this, that would be awesome
The player doesn't want to play some flac and wav files of mine while others play fine. I think it's an issue of my files but I'm still trying to figure it. And lastly, themes! I do miss the theme options of my x1, the ui of the m3k is nice don't get me wrong but being able to change it up is always a nice touch.
Hope that helps, if you have any questions feel free to ask.
Edit- the m3k also comes with a screen protector pre installed