Nice to hear from you again.
The Therapedic models are an excellent value. They are made much like the older Sealy Posturepedics and have no memory foam in them.
They do come in Cal.King and the plush model has been tested under body weight that exceeds that of your parents...and it holds up extremely well. Your wouldn't need a latex topper for the plush, but definately would for the firm.
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