That A3 is beautiful. I've been looking for wagons too (don't want a minivan, and the Grand Prix isn't bike friendly at all). I may put a hitch on my car or its replacement if I get a sedan, and use the wife's minivan for hauling things....but here's what I've been looking at:

Santa Fe - good marks from Consumer Reports, but gas mileage may be weak.

RAV4 - highly rated by CR

New Subaru Forester (I know you want used) - top rated by CR, and fixes Subaru's back seat room issue. The current Outback and prev gen Foresters have really cramped back seats.

If you can find a 2006 or 2007 Chevy Malibu Maxx.....that might be interesting. It's built on the Saab 9-3 platform, has HUGE back seat room (wheelbase is 6 inches longer than the standard Malibu), and it's a GM, so the first two years of depreciation will make it affordable....and CR's rating has been at least reasonable. It's FWD only, but has traction control. If your roads at least get plowed well, it will have no issues. I've driven my FWD Grand Prix in all sorts of snowy conditions without any problems.

I'd stay away from the Chryslers (Pacifica and Journey) unless you found a real steal. Reliability hasn't been great.

Saab and Volvo (9-3 and V50) have AWD wagons, but they'll cost a bit more to keep on the road.

VW has the Passat wagon available in an AWD version. Cheaper than the A3, but a bit roomier. CR doesn't have great marks on reliability, though.

VW also has a new Jetta Sportwagen out now....it's available in the 2.0T version (like the A3), as well as a clean diesel (may not be available yet, though).