Tgrisham,
I believe kbps is a measure of the rate that the bits are delivered over the internet. Stations with higher kbps deliver the bits needed faster over a high speed connection, but I have found this does not necessarily equate to the best sound. Sometime the bits delivered in a slower connection can sound better. The Roku buffers the bits in local memory before sending them on to the DAC to be converted to analog as needed as the music plays.
The fastest stations I pick up with the Soundbridge are 128kbps. I am not certain if there are others available that are higher bandwidth...there very well may be some.
Some stations are available at 12kbs and slower speeds. I usually go with the 128kbps versions, but there have been cases where these do not sound as good and the lower bandwidth versions sound better.
The best stations are indistinguishable from good quality CDs with my rig.
The variety of music available with really good sound quality is almost overwhelming at times. I can spend hours just searching out different stations to check them out. I save my favorites for fast access using the Roku favorite stations feature.
The Roku also provides a web page that you can access from a browser on your network and use to change stations, volume, etc. There is also a Rokuradio.com website that can be used to control your device remotely as well.
It is all very cool and sounds great. The functionality on the web page and site is a bit choppy and incomplete compared to controlling the Roku directly with the remote provided, but it is still very functional and should only get better over time.