I have XM on my bike, an 04 America, with some bass monter helmet speakers. I hear traffic and other noises (my T pipes) just fine, but I don't play it as loud as it goes.
If you go this way, I have a couple of sites I'd recommend for installs.
http://www.xmfan.com (go to XM installations and pictures, then Installing XM on a motorcycle)
http://www.myradiostore.us (for mounts and such)
http://www.2wheelinnovations.com (also has mounts and such)
I bought my bass monsters on ebay.
