Steve,
Bought my Zumo 550 @ buydig.com for $620 - no shipping charge, no tax. Handlebar mount is junk - went with Techmount & so far very pleased. Have had other GPS's in the past - Garmin on the boat, so that may be why the Zumo was very easy to learn. Or it could have been reading the encyclopedia of knowledge d00d (otherwise known as Zumo Guru) has posted here - extremely helpful stuff. Except no cold beer locator.... so far.
Have XM built into the 147 function H/K radio on the bike so did not get the ugly azzed XM antenna. Works great - Aux. plug in on bike for sound & also in one of the cars. I'd buy it again - price seemed to bottom out to about $600 in Nov. & now is a little bit higher. Good luck.
Question: what FM transmitter are you using? Bought one from Best Buy that they recommended & it's junk - will be taking it back.