The software is the difficult part. Making something play music off a hard drive is pretty easy, but doing it well, and tailored for the car environment is the difficult part that so far no-one else has matched the empeg on.

The CarPC route seems to be cram all the features into a program sitting on top of Windows, and expect it to work well. The interfaces just don't work for the car once you get past the initial flash of some, the music capabilities offer much to be desired, and boot times and recovery times from failure are slow.