If you're relying on the tent to keep you warm, you're doing it wrong. Use your sleeping bag to keep you warm, use the tent to keep you dry and bug free.

I have a quarter dome, and it's a great. It's just big enough for two people to share without being one on top of the other and it has huge vestibules for gear. It won't keep you warm, but neither will most tents (Except for the Stephenson Warmlight, maybe).