Hi zman1.
Welcome back to our forum all the way from 2013! 
Sorry to hear that the Restava started sagging and that you had to put up with it for so many years. You’re quite right - a sagging mattress is often the cause of back pains and spinal alignment issues, which can cause the hip pain you’ve been experiencing. Restava used to be a member of this site about 7 years ago, but they changed the designs and lowered the foam quality/density in their mattresses, and after many weeks of attempting to find out the specs of their reworked designs, they wouldn’t provide the information we needed so we weren’t able to confirm the quality/density of their foam materials. Because accuracy and transparency is one of the most important criteria for membership here we’ve terminated their membership. Also, companies that do not have a system in place to honor their warranties are another reason why The Mattress Underground has a rigorous criterion for accepting businesses as members of our community. It is an unfortunate fact that many modern mattresses are using lower-quality materials, lower density foams, and more fibers and convoluted foams that are resulting in a shorter comfort life. That was one of the reasons for the founding of this site – to help educate consumers about quality materials and then assist them in finding better quality manufacturers or retailers.
As you are a hot sleeper and have issues with movement isolating qualities of memory foam you are correct to stay clear of this material. as it has some drawbacks… It tends to sleep hot for those who are sensitive to this and even the newer generation more breathable memory foams are not as breathable or open-celled as latex. Because it absorbs energy, has little resilience, and is a poorly supportive material for movement or other “activities on the mattress” and relies on the layers underneath to provide support and spinal alignment.
While I can’t select your perfect mattress for you, I can certainly guide you in a better direction. What is your weight, height, and preferred sleeping position? Do you have any “deal breakers” when it comes to a mattress? There is quite a bit about the 3 most important parts of the “value” of a mattress purchase in post #13 here which can help you make more meaningful quality/value comparisons between mattresses in terms of suitability (how well you will sleep), durability (how long you will sleep well), and the overall value of a mattress compared to your other finalists based on suitability, durability, and all the other parts of your personal value equation that are most important to you (including the price of course and the options you have available after purchase if your choice doesn’t turn out as well as you hoped for).
Since it’s been quite some time since you’ve been around the forum, I would also recommend reviewing theMattress Durability Guidelines and the Mattress Shopping Tutorial.
I look forward to your reply.
Phoenix