Your efforts to create your own software have to be applauded however I believe that for the majority of incar PC users, the carcomputer is far more than just an MP3 player. The 3 or 4 main software packages being written at the moment include DVD, MP3, XM PCR, FM RADIO, GPS etc as well as an interface for external APPS to be run. These can generally be controlled either via the Touchscreen (big buttons make them easier to use) or via an IR keyboard or keypad.
Also visualizations are provided via Winamp or WMP and there are a lot of downloadable choices for these.
We are always willing to try out new software solutions but designing it from the start to be a univeral control system for incar functions might be better than focusing purely on an mp3 player