Upgrade advice

I have a 2007 Prius with Navigation with 45,000 miles. It will be paid for in a few months, and I really like the idea of saving $400 per month on my car payment. The car runs very well, so there’s no need for a new car. All I really want to upgrade is the audio.

I have the Dice Electronics add-on that allows me to hook up my iPhone. The dealer ran the wire through the small cubbyhole under the radio.

That said, I’d really like to integrate Pandora and NPR stations from my iPhone. I have XM radio, but I allowed the subscription to lapse. I would like a cleaner interface than the giant fonts offered by the factory model.

Are there any reasonable solution for upgrading the audio on a five year old car thyat would no decrease the resale value?

Mike