The reason I have some interest in this is because I'm one of those guys who gets the cheap radio and replaces it. I'm old school so now with all the fancy steering wheel controls, amplified antennas and back up camera it doesn't make it easy anymore. Without ripping into the car more than I want I guess I could add some better speakers and add my own dash mounted GPS NAV. Reading some other forums and watching some videos made me not want to do it. But..... check ebay, youtube with some search terms and maybe you'll hit something. I saw you mentioned RCA adapter.
1- The headunit is pretty good, I am no hurry to replace it.
2- I use my phone's GPS, so I don't need the GPS option. The only downside is that my phone's GPS requires a data connection. 90% of the time, I am fine. If taking a long trip, you can download the required maps ahead of time in case of bad connection locations.
3- CD player. This headunit does not have one. If you want to use your CD's you are out of luck.
4- Android Auto/Car Play. I wish these were on the unit. I can use my phone via bluetooth, but these mirroring programs are much better.
5- Sub output. The headunit does not have one. You have to buy a separate unit that creates a signal for the sub amp, but a sub output is much better.