How much do you need to carry? You ask about large vehicles, but a Forester isn't large. Do you need to carry more than the Forester could?
There are no minivans or largish crossovers with great fuel economy. In these you'll most likely get high teens in the suburbs and low 20s on the highway.
The most fuel-efficient wagon in your price range is the Jetta SportWagen TDI (EPA ratings 29/39). I'd just be a little concerned about reliability, since those in your price range will have 90k+ miles on them. The gas JSW will be less expensive, and EPA ratings are still higher than other alternatives (24/31).
Another good combination of fuel economy and practicality in your price range is the Chevrolet HHR. EPA ratings were 22/30, the highest of the vehicles I mention here except for the Jetta SW TDI. Few people care for the styling, but this makes them especially affordable as used cars.
The Mazda5 compact minivan has more cargo space than the JSW or HHR, but isn't as fuel efficient (22/28).
If you need something much larger than these, then maybe the Dodge Magnum (a large wagon, but without a lot of cargo space, offered through 2008) or a minivan.