The mount position makes a big difference in my ability to divide my attention between road and nav system safely. SW-Motech makes the mount bracket, I ordered it direct from them.
You must be referring to the 750i because the 700I shows up as discontinued everywhere I looked. I think Garmin is getting ready to stop support on it or stop selling it.
I'm all for the XT myself, the 750 looks nice but my GPS needs are only for the bike. The XT provides a waterproof means of charging/powering and operating the unit (via non-contact plate). Non-moto units need to be plugged in via external connectors that are not waterproof or even water resistant while in use.