If a hatchback is a necessity you might want to look into this
http://www.fitfreak.net/forums/fit-c...us-2009-a.html
But, I love my Fit and there's a lot of room for cargo, like you said. The '09 will be a little bigger, but I'm almost positive the Matrix will still have it beat in terms of cargo space. I can't relate too much with the dog issue, because I own a Chihuahua and he fits in the glovebox, j/k.
The Matrix was something I was thinking about getting for a second car. the only issue I had was price after you upgrade from the base model.