I had an 1100RT with BMW radio as my previous machine. I appreciated the radio.
Has your RT got the radio remote controls already? If not, you have a lot of hard work ahead of you. The in-built speakers are useless at speed in any case, especailly if you wear earplugs.
A more realstic and versatile approach approach would be to be to buy an MP3 player/radio unit, stick in a tank bag and run it up to the helmet with a simple earpiece.