XM is hooked up with Directv and Sirius is hooked up with Dish. We have Directv, and the Broadway channel is not available on our package. There are certain channels that require a higher subscription level.
XM does put its music channels online, but they aren't free. I don't know if you can do an online-only subscription or not. If you have one of their radios, you get the online part automatically as part of your regular subscription.
I'll admit up front that I am biased, but I find the mix of tracks on XM's Broadway channel virtually unlistenable. They have some excellent interviews though. I wouldn't recommend XM if your main interest is getting a Broadway channel.
Zack
Pass it on - Take a kid to a show.