I did the poly fill and replaced my head unit with a Sony MEX-N5100BT. The sound quality is noticeably better, but I still plan on replacing the speakers as well. One of things I liked about the Sony unit (I'm sure others have this feature as well) is that you can change the color of the display. I set mine to white and green, which ties in nice to the Jeep's display and my CB Radio. Bluetooth, hands free phone operation and the ability to control the head unit through an app on my phone are a few other nice features.
I ordered through Crutchfield and will be getting speakers from them as well. Great service and price.