I have a similarly butchered 80gb ipod, the fact you can now pack 4 x 256gb cards in there (in theory), is quite amazing. I use a pioneer head unit that pulls audio off the ipod digitally, so it's essentially an easily navigatable storage device that I can control from the head unit screen. I'm limited to lossless cd quality, but that will dobehile I'm driving. The head unit will also do flac off usb, 24bit 96k max, but the navigation I find less intuitive. I'll probably replace this with something RPi based next.Apple ipod with quad sdxc card conversion here for mobile use. My samsung s20 sounds better via Bluetooth in the car than the ipod on aux though. But ipod is much better with in ears, go figure.
Bought the daughter a Fiio m3k for Xmas last year and I though it sounded good for the money. Better than my 6gen 80gb ipod.