Hi Dldlaw,
While it’s good news that you were successful with your warranty claim because many aren’t … unfortunately there really aren’t any particularly good options available to you if you are limited to another Simmons mattress.
There are some suggestions in post #2 here and the posts it links to that may be helpful for those who are in the unfortunate position of needing to make a comfort or warranty exchange when the only options they have available are a major brand that uses too much lower quality and less durable materials in the comfort layers of their mattress.
It’s unlikely that you will find a replacement mattress that doesn’t have an obvious weak link in the materials so it will really come down to choosing a mattress that is a good match for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) but will likely have the same issues as your old mattress in a relatively short period of time or choosing a firmer mattresses with the least possible amount of lower quality materials in the upper layers and then adding a higher quality topper for the additional pressure relief and comfort you will probably need.
Phoenix