What OS are you going to use? I suggest tinkering with a linux distro and grabbing DashPC specifically
for car usage.
This is just plain 1337 I don't even have a car yet, but thats a sweet idea you got going there. Make sure if you run linux/windows you have a nice speakers setup w/ plenty of base! I would get an Audigy 2, or one of those high-end Hercules cards! Some ideal applications for both operating systems are:
Linux:
XMMS 1.2.7 (The BEST mp3/ogg player)
mplayer .90 stable (The BEST movie player)
DashPC
LIRC (For your infrared remote)
Windows:
Winamp 2.91 Standard (Lightest on resources, while owning and having the ability to play ogg's :)
WMP 9.0 (There *are* other good movie players out for windows, but I have had the best luck w/ media player 9 so far)
It's important to have a fast, and extrmemly stable OS. When bluescreens are simply not an option, one must pick a later if not latest revision of the microsoft operating system. I suggest Windows Server 2003 Standard Edition. It is the fastest, most stable, and most secure OOTB M$ OS that ever saw light. Now if you don't know where to obtain this, or don't have $2000 bucks, this is where linux comes in handy. A speedy thing such as Gentoo, Yoper, Morphix, or any other distro known for speed, specifically i686 compiled is what is for you! Now I wish to say good luck, and let the moddiifications begin!
EDIT: Winamp 2.91 Standard, and some wicked high-quality (320 kps oggs) are available from the site in my sig... I bet that those ogg's would sound stellar in your newest 'box' hehe.