The Carista MIB2 fitted to my Polo GTI+ (and recent Golfs, I believe) will take MP3s and FLACs from an SD card or USB stick formatted exFAT.
I download as it's quicker than ripping a CD. Usually the download comes with artwork. No biggie for me on the rare occasion it doesn't.
I just have a folder for each Artist, with album folder within, and the FLAC/MP3s within that.