I'll chime in here since I have the K9.
Excellent little player. Took the microSD card from my X2 and popped it in, no problems all files visible. Feels really solid, no rattles and the buttons have a nice tactile click.
There's no input lag! This one really surprised me but going through the menus and folders the navigation is quick and there's no delay. Also has a custom EQ. Yep. Screen is actually usable outdoors and can display album art when playing.
Been using solid for the last 2 days and haven't had a single glitch in the sound or UI. Only thing I'm wishing for is dedicated volume buttons but I can live without it. My X2 has been retired and hopefully sold already.
Best thing about this is the price. If it breaks in the first month I'll just buy another one or try something else. Amazing what you can get for $25 these days.