din/double din/half din, control interface and preamp

im surprised theres no USB dac with a 4-5 volt preamp available.

what would be nice is to have a replacement for your car stereo
something you can put in place of it.

that has the following features

1 hardware volume control
2 small display for track and other basic info
3 hardware playlist controls such as play stop fwd rev pause mute etc just like normal car stereo
4 bass treble controls
5 inputs and outputs for 6 channels( front rear sub)
or internal DAC + preamp that splits the channels into front rear sub RCA outputs

about no 5....

sub is not as important to have split up in front/rear or left/right as the tones do not contain any directional info, so it does not matter where the sub is placed... under seats, trunk etc will be all the same

you shouldn't be surprised. there are many different ways to connect a carpc to get audio, and none of them are the same, so it is hard for companies to justify the cost of building a product that a niche of a niche could really use.

for instance, i don't need 2-5......

it sounds like you really want a hu anyways-- try looking at the car2pc interfaces. they support some alpine and pioneer units that would allow song data to be displayed on the hu.