First off I have a stock height Clearview sheild on my 09 RG. That alone cut down the wind noise on the highway. 2nd, I installed Hogtunes and the clarity as I turn up the volume is amazing and on the highway @ 70 is no problem.
Hogtunes I think has an amp as well, that you could add if you wanted it, but I think you also need maybe a mounting bracket from them as well (not sure as I recall some bracket needed to mount the amp for a RG, just not sure of the year).
The auto volume control works fine for me, but I think it's the combo Clearview and Hogtunes.
Ride safe and have fun!