New mattress advice

HiWe want to change our double mattress as it is 9 years old. You have been recommended by my sister who bought a mattress from you a couple of years ago.I an 5'3" and 68kg and my husband is 5'10" and 75kg.Our bed frame is a wooden slatted frame and our current mattress is a Sealy Posturepedic Balmoral.ThanksSue