I'm looking at a Garmin GPSMap 478 to take the place of my StreetPilot 2820. I've decided that I ride in the rain and whatnot so much that I really want (need?) the Nexrad radar overlay you can get with the GXM-30 antenna. My questions are... 1) Do I need the "motorcycle power / audio" cable? Or just the included "power / data" cable? 2) I've been using the OEM BMW Nav III mount. It's the Garmin "motorcycle mounting bracket" for the 2820. ...with a BMW kit that mounts to the screws that hold your handlebars down on top of your triple (similar to the Touratech bracket shown below). I think it's the same mount for the BMW Nav II/III/Zumo. The 478 doesn't have a "motorcycle mounting bracket" like the StreetPilots and the Zumo, so I'll probably have to get the Touratech mount. Would this: and this: http://touratech-usa.com/shop/media2/01-065-0087-02.jpg?-session=touratech:0C68DDEF13f9014BDAlrp19E36E7 Be the right answer to get it securely mounted in the same place? 3) Data Cards The 478 comes preloaded with City Navigator NT and Marine Detail maps. I've never used anything other than CN NT on my 2820 so I'm not worried about adding additional maps. However, are the waypoints and routes stored internally or on data cards? Do I need one? If I do need a data card, are the data cards proprietary or can I use a Sandisk 2GB SD card (I know it's not an SD card, but I'm using this as an example) I picked up at Costco for US$35.00?