I was in the same situation a few months ago with my new to me RS6. Looked at going the RNS-E route, but ended up with the Pioneer AVIC-6100NEX. Very nice unit and with the trim plate for an A6 the installation looks very professional. Tried using the shark fin antenna, but was getting quite a bit of noise through the Sat antenna as well as lots of cutting in and out. Bottom line is that I put both the GPS and SAT antennas that were included in the kit on the front dash, and since my dash is black, and they are both very small, they don't stand out at all. If I ever decide to sell the car, it will be fairly easy going back to stock. I'll try and post some photos in the future.
The sound through the stock speakers is quite nice and the Bluetooth connectivity for my Droid Turbo is seamless. Great upgrade.
I have sent you (Other_Erik) a PM. Thanks!
2003 RS6, Mugello/Silver, MTM Stage 1 ECM, and TCM mod, Abt 19 inch wheels for summer, stock 18s for winter, RS6+ Pedals INSTALLED! 2Bennett coilover system, 2Bennett front brakes; DRC gone!
In the end I upgraded with an aftermarket Pioneer AVIC F70DAB, and installed a back up camera, still works with the factory amp and subwoofers and sounds brilliant.
I am getting a problem with my rear brake lights now though! Not sure if it's related to me taking out the old Sat nav and CD changer completely, or the rearview camera splicing into the reverse lights??? Problem is only when I turn my lights on, and then I get a brake warning light, and i lose power momentarily. Bit scary at first.
But the warning chime is the worst, as it's every 30 seconds or so!
Anyone had this before or have any knowledge in fixes?
Cheers, stay safe.
2003 Audi RS6 C5 Avant Black with 19's