Rockbox uses DUMB, I believe, which is a nice replayer, but there are still lots of tweaks that should be done to most tunes to make them sound "nice". I use multiband compressions, 31-band EQ, hand-drawn volume envelopes and even multi-channel mixdown in my mastering.
I can also fix bad songends (cutoffs, etc) and custom-set the panning on amiga mods. DUMB is nice but mastered is better