I had just about the same requirements, wagon, awd, fun, somewhat to pretty reliable. I too looked at the V70R, but go read the forums... HORRIBLE reliability, and I mean bad. You think Audi and BMW will be expensive to maintain, that car is awful. Good in theory, bad in practice. So like others said, best economic sense will be a Subaru (and turbo for fun). The WRX are pretty tiny though, I would get a legacy or forester if you actually want the wagon for room. If you want something a little less reliable, and more comfortable (with FRAMED windows) I would look to Audi (over BMW due to the better AWD system). A4 is okay, but if you want fun you can find an older S4 turbo in the 10-20k range but I would prefer the V8 for reliability and cost to own I think. Not sure if it is true, but I would assume two turbos + Audi = $$$$, and the V8 would be a little less in the overall ownership cost. A6 is a little bigger again, the rear seats in the A4 are small for adults (6' range). Other than that, there is not too much that is interesting. I would love to see a fusion wagon with the ecoboost motor, or CTS wagon, but American car companies drop the ball with wagons.
And if you ask what I ended up with... a 2003 2 door Civic paid in cash. It kind of sucks, but is super reliable and paid off. Oh, and the girly bought a 2006 A6 wagon so I can ride in that!