Since it's going in a cab with mala, I'm guessing it's a safe bet that you won't be running a touch screen.
I've used JRiverMediaCenter for ages, and they're MP3 tagging, conversion and searching etc is top notch.
If you use it on a server or Home theater PC, it's great. But the touchscreen skins aren't really that great on an actual touchscreen.
However, JRMC on a cab with a trackball and a few buttons works surprisingly well, esp if you take a bit to find a decent skin and then alter it slightly for you purposes.
If you DO run it on a touchscreen, AlbumPlayer is a fantastic app. It's screens are VERY touchscreen friendly. It costs a few $, but it works welll for playing tracks, and it's easy to navigate for novices. However, it's not particularly good at organizing or tagging MP3 files. For that, I'd definitely fall back to something like JRMC.
AlbumPlayer works equally well on a non-touchscreen, however, and it's got some very well done skins available.