No, I havent bought a radio yet. Its for my father in law for father's day, and before I get glossed as Lawboy Jr, he's out of town until the end of the week so I have a little extra time.
I see on the xm site its 50 bucks for the unit, 50 bucks for the adapter (20 if I get a panasonic), plus you need to buy an xm ready radio.
Most kits come with the antenna; the adaptors are usually if you plan to use it differently than the kit (like a home kit for a car unit). Most kits today are the tuner and antenna (tuner works over FM radio). I fyou want to move the tuner between your car and your house, you may need an extra adaptor (which will include an extra antenna and power adaptor).
I have Sirius and have had it for 3 years or so, love it.
I too would recommend Sirius. Better channels, better music. Look into an Alpine cd player/head unit. I've been in the car audio business for along time and Alpine still has the best user friendly plus quality radios.
Gotta say, for the buck, you can't beat the XM Roady. I have mine here in the office and it runs all day through the Maggies, then when I want it in the Viper, it plugs right up and I go with it. Antenna is dble-side taped against the dash at the windshield on pass. side, cables route through the MGW ashtray (drill out the bottom hole), and the whole thing is neatly out of the way when not in use.
The input is throught the Alpine ACC input. XM rocks!