I bought the module for GPS/navigating for my Kenwood, but uninstalled it.. sold it. It was $800. As Ryan well puts it, I have a navigator each year for the next 4 for that money. Makes no sense to have to repay big money for updates on top of the 800 dollar purchase price...
I have the digital TV module too, tv on the fly is good.
Seeing as though you are keen on keeping the RF, then you may have to spend more.. or alternatively, remove the lot and sell it and make a better system, like Ryan's when money is not an issue...
I never had the luxury of an RF system... but I would say my current system is loads better than an OEM RF system... so you could do better in time.
Enjoy having the RF, they sound much better than the paper cone junk and single cd headunit of my ES !!!
Good luck