I have the Sportster Replay in the house. It came with all the parts to have it installed in the car, I would just have to have that done. But now that I'm thinking about it, would it be alot of needless trouble taking the thing back and forth? Would an in-dash Sirius receiver be less trouble?
Like I said, I already have the Replay's parts. And if I got an in-dash unit, I'd be paying for two subscriptions.
If I got the Replay dock installed in my car, I don't see myself hooking it up unless i was going on a road trip or something. As far as running errands, short trips around town, stuff like that, I have cds and regular radio. If I had an in-dash, I'd listen on short trips.

What do you guys think would make more sense?

If you don't mind paying the additional $6.99 for the second subscription, that's your best choice. Especially, if convenience is important to you. A lot of people just pay for multiple subscriptions so they don't have to move their Sirius receivers around from one place to another. That can get old fast if you want user-friendly electronics. Just do it. Don't overanalyze it. You're missing some really good entertaining. Good luck.

Either the Xact Visor or Sirius One would probably suit your needs. I have the One in my car and I love it.