GTM-20

The GDB-50, which is the MSN Direct receiver, will work with devices that support the GTM-20. You can plug a GDB-50 into a C550 and it will receive MSN and act like a C580. I have done it and it was interesting to see the traffic icon change to the MSN Butterfly logo and have the temperature display at the top of the screen. However, MSN Direct is shutting down on January 1, 2012 so there is really no point in subscribing now.

Not sure what you mean about traffic report? It doesn't speak to you, if that's what you mean. You get an icon on your screen which will turn from Green to yellow to red. You can touch the icon and another screen will come up with options in it. I have that exact cable. Mine is lifetime. Never heard of buying the Cable twice. Might be wrong there, but seems like a redundant idea

The traffic you receive is dependent on the area you are in and if any stations are transmitting the traffic alerts. What I have found is that they are truly a joke where I live. They are inaccurate.

I live in Northern California. There are no traffic alerts here. If I go to Sacramento there's a signal but there's no coverage at all north of there. Since I live 100 miles north of Sacramento and cover the northern third of the state for my department there's no point in having the service. I guess if you live in a city it could be useful but, for me, it's totally pointless. I'd guess that, for a large portion of the US, it's not of any value at all due to a lack of coverage.