my guys have a really firm mattress hungarian duvet quilt. It has some plush pillows as well but they never stay on the bed. There is plenty of room for both to spread right out and yet still be far enough away from each other so as not to disturb one another....oh wait a second...thats MY bed I just described...but its theirs too lol.
Seriously though, they do have a bed that we use as a toy box b/c they like the couch or the chair better, or their first choice, a nice warm lap. I picked it up at wal-mart for like $40, I have had more expensive and nicer looking beds for Quincy but they never got used. I didn't even buy Ruby one, figured its money wasted when she has figured out the luxery of ciouch, chair or my bed.