Is there a perfect king size mattress for overweight persons?

Have purchased 2 king size beds in last 2 years and hate them both. The first was memory foam.... hurts the lower back...can't move feel suffocating. Next was a firm pillowtop which broke down in less than a year. One person is 350 lbs and other is 200 lbs. We love our queen size serta in the guest room but king size beds seem to be a horse of a different color. We tried expensive thick feather quilted pad which helped for a few months. Hubby says must get a new bed today!