With the stock unit (early R53) I can hit the power button on the stereo and it'll play music for a half hour or so while the car itself is off, even without the key. This is part of what has kept me from getting an aftermarket head unit but I'm really missing having bluetooth lately.

I've looked a few places but I can't seem to find a solid confirmation on if the ability to use the stereo with the ignition off is retained with an aftermarket head unit. Anyone with an R53 and an aftermarket head unit able to confirm this?

Best answer I got from crutchfield was "I don't see anywhere that says it wont" which, is just not helpful in the slightest...

 

It is how you set it up but will require adding a toggle switch. Most won't function like the stock unit so it is best to live with having to have the key in and switch to ACC. For my campers I add a toggle switch so I can play without key until the battery is dead if I let it. I don't see it as a necessity for a car like Mini.

 

I am no audiophile by any means, but I believe that you can add an aux input to the stock system and run bluetooth through it. I have read posts that say so...

 

True - but you can also get a better head unit with this (and other) functionality built in.

 

I will bet that even the cut rate HU for $79 at Walmart sound better and infinitely better than retrofitting BT to the stock HU. Again to OP. You know the Mini has a ACC position right? You do have to leave the key in and switch to ACC position with aftermarket HU, and you can play util the battery is dead.