Your set up sounds similar to mine.
I am running winXP Pro on a mac mini solo upgarged to 1.25 gig ram and 120 gig hard dirve.
I have the carnix p1900 ver 2.2
I am using FrodoPlayer and have XM direct. It is working GREAT! except a few things. The Carnix wont turn on mini, but on the carnix site they talk about it needed to be reflased and that should fix it.
Using a garmin GPS and nRoute as my GPS, need something that is mote touchscreen friendly.