I have a Contour 1080HD, Garmin 705 and DashWare they work great together.
Now as far as the Contour 1080HD GPS if you want GPS you will need to leave the camera on the entire time which isn't really practical.
On a 3-4 hour ride you will need to change battery at least once.
I prefer to turn on the camera when I want and leave the GPS on the entire time, and you can use the Garmin for more than just bike rides.
Are you willing to leave the camera on the entire ride to capture GPS data even when you don't need video?
An the Contour 1080HD GPS is replacing the non GPS model so prices are very good on them if you can find one.