I have the Zumo 550/GXM 30 setup and use the CycleGadgets antenna mount - it's an angled metal mount that sandwiches between the Zumo and the ball. You then just pop the antenna on the mount. The magnetic base is enough to hold it on, or it comes with a couple of screws to reenforce it it you want. I switch the Zumo and antenna back and forth between bike and the Jeep almost daily, so the magnetic base works great for me.

Sound quality via the external plug is excellent. No complaints. "CD quality" is in the ear of the beholder. I'll just say that it's crystal-clear, no static or fuzziness at all, except when there's LOS issues (as in, parked two feet froma brick wall to the south).

My only regret with the GXM 30 is not buying it sooner. For the iPod fans out there - I've never used my iPod on the bike since getting XM. There's just alway something on you want to listen to, the interface on the Zumo is very easy to use (easier than the damn iPod wheel), and though you can listen to "what you want, when you want" on the iPod, the problem is you ONLY have what you've got. There's just an incredible variety of stuff on XM.

We're picking up a couple of new Dodge vehicles next year, and both will have Sirius. Lookingforward to having Parrothead Radio!

Personally, I don't think the FTC and FCC will approve the merger for anti-trust reasons. One company in control of the entire market? Can't see them going for it. Plus, I think the competition is good.