Just a little update on my search. I looked at the "carputer" option, in fact, I've had a bit of a desire to do that for a long time. But it really seems to me like they're only worth it if you want to go "all out" and have it do everything, music, movies, GPS, etc. If you want something like a full-up navigation system, like the retail units that are thousands of dollars.
I don't spend enough time in my car to care (much) about that, all I care about is music, and GPS/Nav would be cool, but definitely not must have. Further, it was looking to me like bare minimum the carputer option would be about $700, about $400 for the PC and another $300 or so for the touchscreen, plus all the work to get it working like I want. All for just listenning to music, generally just on my drive back and forth to work, and around town.
So I went back and looked at what was really important, that being to be able to listen to my music without messing with CDs, and with that and the ~$700 pricetag (for a carputer) in mind, I went off and did some more investigating, and I found a head unit I really like the looks of:Eclipse CD7100
The specific features that appeal to me are the USB connection so I can connect up a large flash drive, or hopefully even a USB HDD full of my music, and access it directly from the deck. Of course there are a few other things that make it really cool (to me
GPS/Nav - Very cool, being able to see GPS position, speed, direction, speed sensitive volume.
7 - band parametric EQ or you can get the microphone record the reponse of your car upload it to the EiSERV website and get a custom filter to download to the unit to correct for the car.
Only downside is that it doesn't support lossless audio (other than CDs), but being practical about it, the car is far from a critical listenning environment, and maxed-out WMA should be fine.
At the moment I'm just waiting to get my hand on one to see how I like the interaction before I order/buy one.