Brad, maybe it's just me, but I don't think moving up from an Outback Sport is enough of a big deal that you need to proclaim it on your license plate.
If you haven't thought of anything to put on your plate yet, don't worry about it. Get a regular number plate. I haven't put personalized plates on any of my cars because I haven't thought of anything important that I want the plates to say.
That's my advice - save your money until you come up with one that means something to you.