I have the the Zumo 550 that has XM, Bluetooth & MP3 on it. I have the GXM30 that feeds through the Zumo. At this time I am using a 3.5mm output that goes into the factory radio by way of the aux jack on the back of the factory unit. I can use the BMW controls to adjust the volume but it does only go to about halve the volume that the radio will reach. This allows me to listen to voice commands, XM and/or MP3's.wilbar00c said:How do you plan to feed the XM GPS output into your helmet? On my 2730 XM feeding into #1 cable on Baehr unit with a special Baehr cable, my volume is limited, when I use custom ear plugs. I have the casette radio, so I feed into a cassette adapter and use the cycle radio volume control with the XM on 100%. I can mute it quicker then getting to the small mute on the GPS XM face panel, which takes at least 2 pokes!!! The radio control gives me all the volume I need.