I'm thinking of connecting a generic AC adapter to my Sirius Sporters 5 radio. I'm not sure of the output specs of the receiver (havent got it yet) but my main concern is interference resulting from the AC adapter.

Has anyone connected on or are you using the one that came with the Home Kit?

it will either be 5 vdc or 12 vdc. I think all the modern radios are 5 vdc. i don't think the ac adaptor will generate any noticeable noise unless you get a poorly made one without filtering.
You could get a regulated power supply from radio shack that has the cigarette lighter socket on it and just plug your car lighter cord into that. those power boxes are pretty cheap.