In reply to Duane: I have the Airo 180 and it's pretty comfy, no complaint for the 2 season camping I've done with it.
I'm thinking of getting the ME Helium 3.8 for colder weather, and would think it's probably a safer (comfier) bet, especially if you've got the car. Although space is a premium, look at the spec:
Alpkit (packed) - 28 x 13cm 653g
ME (packed) - 27 x 16cm 750g
Little extra size/weight when it's packed but quite a lot more padding when you're on top of it!