I've got an old classic car, with a din size hole down low near the gear shift and a massive gap between the centre console and the dash. My life is ipad iPhone centric, and I don't like learning all the complexities of some complex stereo, so it seems sensible to use the massive gap in the car to install ipad / iPhone mounts and make everything run by ipad / iPhone. But I do also have this din slot, so an option (or the obvious option ) is to install a din stereo with good iPhone integration, and install the ipad above that. Then at least I have basic stereo functionality if I take the ipad out, but generally I want to do everything via the ipad. I'm not overly fussed about having a CD slot.

Anyway, one thing I'm confused about with all the stereos that allow plugging your iphone into USB is whether they force you to play music through the stereo, by selecting everything through the crappy LED display, or whether you can play the music through the iPhone music app, and the stereo picks it up. I even read the manual for the Sony MEX-gs600bt, but it wasn't obvious to me what the answer is. I definitely want to play music through the ipad controls, preferably the inbuilt app, rather than some proprietary app. It would be a nice to have, to have 2 USB slots, so I could plug in a USB of music too, but that's not essential.

What din head unit would you recommend for this? Price doesn't matter within reason. I don't see any point getting anything super complicated, just for the reason I'm trying to push the complexity into the ipad, and something with (say) some massive pull out screen running android or something would miss the point.