Sirius vs. XM network radios

I need to know before I buy a replacement radio:
I have noticed that all the "good" radios sold in store anywhere operate on the XM network. Since I drive in rugged terrain a good deal of the time the XM network is not so good for a good constant signal. Only the cheap featureless Stratus 7 is sold for the Sirius network. I know that the Starmate 8 is still for sale but I get the impression that SiriusXM is trying to get people not to buy it because there are no extra channels available, and the very fact that it is more difficult to buy. If SiriusXM is going to eliminate the Sirius satellites this will be a problem. Does anyone know what is the deal here?

Thanks!