http://www.sonicelectronix.com/item_91069_Pioneer-AVH-170DVD.html another option with newer features.

and the preamp voltage isn't a big deal. sure if you are using high end sound quality subs/speakers/amps then you may see the difference but in your situation it's a non issue.

also true, but non the less if he is skimping out on quality gear he may go cheap with wires and instalation techniques . thus creating some bad signals.

i always try to go above 3 volts. the sound is not louder but the signal it gives out is generally cleaner. i mean you can always do other things to get rid of distortion signals by adding more electronics for that purpose or you an get a decent headunit that gives a good signal.

and i would say pioneer is probably one of the best headunits out there today and has been. ive always been a big fan of their headunits.

Unless the amplifier is garbage for the subwoofers 2v is fine... All you're doing is gain matching so it really shouldn't matter. I'd go anything Kenwood/Pioneer for double dins.