I'm actually in the process of installing my 2G surf under my passenger seat also. I eventually might break down and get an ipod but as you mentioned its all about budget right now. I have my eeepc connected to my stereo aux probably as you do..only mine is connected to the front aux for now. I decided to output my eeepc display from the VGA output to an rearview mirror/monitor. I control my music with XBMC software (on Linux) and a wii remote using bluetooth.
See my post: http://www.mp3car.com/vbulletin/work...box-mount.html
You might look into connecting you iphone to an external display if you have the touch. See these posts: http://www.mp3car.com/index.php/174-...-your-PND.html