I bought the Garmin Zumo 550 awhile back paid $750.00 for it, have to say i'll never do that again.

One of the main selling features at the time it was water proof.Have had great luck with it and it has never let me down. They say the 665 has satilite capabilities for weather and radio and i saw it $100 cheaper than what i paid for mine..

I learned that if you want a nice cheap GPS go to your local tow truck company and ask the drivers if they have any for sale, you'd be surprised what they have for sale. Powerlet makes all the adapters for the Rocket III.
http://www.powerlet.com/shop-by-vehicle/triumph/2005/triumph-rocket-iii-2004-2009/15/433#formtop