I had the same question, iTunes does what it's supposed to do almost perfectly.
I tried many options (Amarok, Clementine, etc.) and found the best option is to use iTunes itself, then browse the player by <Files>. You set iTunes to use the RockBox player as the music database path. For playlists, I use the playlist editor Strawberry to make and edit playlists that RB can understand (meaning relative paths).
I wrote a small program (bash script) to convert the playlists that RB natively creates (absolute paths) to the one that both Strawberry and RB can use (relative paths).
This way, you're limited to browsing by Artist>Album>Song, but you can use bookmarks, which isn't possible in database mode, and iTunes keeps everything organized.
I'm not aware of any other options myself, but I'm open to trying. I use Mac/Linux.