How big of a dog/crate?

My folks have a rhodesian ridgeback/black lab mix, I think it's bout 65 lbs, and my mom ended up getting an MDX to have suitable space for the dog crate.

Although the other day I did see a Forester driving around with a similar sized crate in it, just with the seats flipped down.

If you are inclined to take both the dog and more than one passenger, you'll probably need something bigger.