Got a pair of Sena SMH5's for Christmas. Seem to work pretty well when testing, but haven't used on the road. You can pair with GPS or phone, depending on how you plan to use navigation. Been using Waze for IPhone and really like the app. Get voice directions and listen to music on phone. Haven't paired with my Garmin, but pretty sure it is a simple process if you plan to go that route. Not sure if you can pair both GPS and phone at same time- haven't tried.
Was a little disappointed with the music sound quality of my SMH5's in my Scorpion helmet. Planned to use the Sena's mostly for communicating, but you also have the ability to listen to music from a paired device as well as using for telephone or intercom.
For the price and quality, its going to be hard to beat Sena.