I got my Zumo a year ago for $630, and from what you describe it is the GPS you want need. You can prob get them for lower than that now.
The 2610 is a great GPS, but does not have all the features you want. You wont be disappointed with the 2610 unless you really want the XM-Bluetooth capabilities.
The Nuvi is not shock or water proof I would be very hesitant to put the Nuvi through a motorcycle ride. But they are great car GPS and other than not being good for a bike you would not be disappointed either.
'06 DL1000 Farkled