What have you found is the most comfortable portable bed for tent camping?

Trying to figure out a comfortable bed solution for tent camping. The best I've found so far is using a Thermarest 1.5" inflatable mattress and a layer of 3" thick open cell foam over that. But I'm not totally happy with it, as I still wake up kinda sore. I guess I'm looking for the best thing short of an actual bed mattress that can fit in the trunk of my vehicle. Thanks for any good tips.