You could leave the stock radio alone, and use your smartphone to stream music into a Digital Signal Processor with a built in amp via bluetooth and then on to your speakers which can be concealed or not.
not a fan of that. we currently have a radio under the seat of our dart. while it works via Bluetooth to the phone, its kinda a pain in the ***. just cruising around town it might be ok but on a road trip when you are running maps phone etc with your phone it would be much easier to reach to the dash radio and increase/decrease the volume. i found this out personally on our recent 5000 mile road trip.
I'll be using these guys to modify my stock radio. Home page MikeHaganAntiqueAutoRadio.com. a friend has one of his radios in two cars and loves them. not cheap but what is these days.