I'm going to echo a lot of what other people have already said: First, buy what you need now, not what you
think you might need. Life throws a lot of surprises at you, and do you really want to carry around an over sized, overpowered, over outfitted expensive car for several years on the chance you might need it in the future? If you
want an Impreza, that's another thing, but it might not be good to convince yourself you need one based on what could happen down the road.
With only two people, and the need for occasional grocery getting, a Toyota Echo, Yaris or something similar would probably solve your needs just as well. As someone else mentioned, depending on how in-frequently you use the car, and depending on availability in your area, car share (Zipcar, etc), might be a better idea financially.
Second, you mentioned wanting space for dogs. One thing you didn't specify was what kind of dogs we are talking about. If you happened to have a Great Dane and an English mastiff, I might concede that you need a larger car.. if you had two Chihuahua's on the other hand, maybe not so much. But again, you don't have any dogs right now.
Third, while it might be nice to have, I don't think AWD is at all the necessity people make it out to be for winter driving (this is from someone who grew up in Ontario). A good set of modern winter tires really does give you good grip, especially if you are spending your time on well maintained normally plowed roads. If you were planning on going off roading and think the situation might come up where one drive wheel is stuck in muck, then it comes in handy. But the former happens a lot more than the latter, which is really marketing material.
For context, we have a late model Honda Fit (bought used, but I'll concede that was difficult and I considered buying new given the price differences), two small/medium sized dogs (15 lb each), and for regular use we have an abundance of space. We can also easily go camping and usually have enough space for us, the dogs, and provisions. Not knowing much about kids, I say with a grain of salt I could easily see one carseat, and maybe two fitting in and still leaving room for the dogs and us. For two kids, two dogs, two adults, and gear for camping, that is what the roof rack and hitch storage are for :).
This might also be helpful:
Turning a Little Car Into a Big OneFor what it's worth, I've never owned a Subuaru (rented once and liked it, but a bit of a gas guzzler for my taste), but the people I know who own them do quite like them and have had good experiences. We have bought two used Honda Fits, both from Subaru dealers coincidentally, and have found the dealerships a pretty good experience.. and I think it is tough to find a car dealership a good experience :)