Ideas to put to use the entire double DIN space?

[phantomlord]

I want to replace my factory Toyota T2603 double-din (180mm x 100mm ) stereo, mainly because it does not seem to have an RCA input for an MP3 player.
I know there are a lot of fine single-DIN stereos around, but I am not too enthusiastic about putting a filler and instead, I was wondering which would be a good budget double-din stereo or other car entertainment device?
I'm not interested in spending a fortune and my main requirement is being able to listen to my audio book library in the car, so mp3 playback from SDHC or USB and decent 4 channel amplified audio output are fundamental.
Besides that, I don't think I would watch movies and I definitely do not need GPS as I do not travel very far with my Yaris (Vitz?) 2006 4-door sedan, so a big screen is not necesary unless it fits a budget of around $250?
I would spend more, but only if anybody knows of a decently featured car computer with integrated screen that would fit in there? Does anybody run Android OS or even MS Windows in their dash?
Experience or suggestions are highly appreciated.