I know many of you have purchased the ZUMO 550. I just did today for 400.00 couldn't turn it down even though it was used. I have a question. When using the XM radio function can it be used via bluetooth or does it have to be used by plugged wire. I dont know if I should buy a new helmet with bluetooth or just buy a headset that plugs into the unit..Anyone with expierence with this unit please help....