I too have a refurbished Intel Mini, and based on my experience with this system, as well as recent Macintoshes in general, one thing I'd be wary of is the audio output connector. I belive it was likely a problem with that connector that prompted the return of my Mini in the first place-- And Apple never completely corrected the issue (audio cutting out if the connector/cord is jiggled).
I too secured an excellent price for this machine, and based thereon I never opted to return it to Apple, choosing to just live with the problem. But that said, I haven't yet installed the system in my car, and I've intention for it to be removed each time I leave (by way of a dock I'll custom build)-- Much like the older car stereos that you used to completely pull out of the car and take with you (prior to the faceplate-only idea).
Because of the fact that I'll be removing the Mini and reinserting it frequently, it's a certain bet that the audio connector is going to outright fail; and quickly. Because of this I bought a Griffen iMic-- A USB sound "card" (
http://www.griffintechnology.com/products/imic/). With this I'll be able to run my audio through USB, never having to use the poor quality onboard audio connector. It also facilitates, as the name implies, the connection of a microphone which I've intention to use in issuing voice commands to the Mac, just for fun.
Anyway, beware of the audio connector on these machines!