you can use any of those three hooked up at home, the difference is in their focus. The Skyfis are designed specifically for easy in-car use, while the Inno and SkyFi3 are designed for varying degrees of portable use. Your decision is pretty much based on what your primary goals are:
Listening live in the car: SkyFi2. Pros: Large display and large, easy controls, 30 minute pause buffer. Cons: large unit, difficult to use portable without the skyfi boombox. Must be in a cradle to function.
Listening live in the car, and recording content to listen to later in any location: SkyFi3. Pros: Large display, some controls to make in-car use easier, 70-minute pause buffer + 10 hours recording, MicroSD slot for MP3s, recording schedules, battery portable. Cons: no live XM reception when undocked without additional equipment (antenna headphones + larger battery pack), limited recording time.
Listening live on the go, and recording content to listen to later in any location: Inno. Pros: color display, self-contained portable live XM reception, 30-minute (I believe) pause buffer, recording schedules, 50 hours XM or 25 hours XM + 512MB MP3s. Cons: small display, no direct tune controls (even on cradle), no extra storage option for MP3s, choosing to have some MP3s cuts XM recording time in half.
Any of these can be used in the car via an FM modulator, either XM's crappy sureconnect, or you can use the far-superior FM Direct adapter
. This is what I do with my SkyFi3.