Hi whiterose,
Welcome to the Mattress Forum!
I’m glad that the information here has been useful to you. Just in case you haven’t read it yet, the first place to start your research is the mattress shopping tutorial here which includes all the basic information, steps, and guidelines that can help you make the best possible choice … and perhaps more importantly know how and why to avoid the worst ones.
The Brooklyn Bedding Best Mattress Ever (BME) comes in three different firmness choices and uses good quality and durable latex and polyfoam materials that would generally be suitable or any weight range. Brooklyn Bedding is a site member here, which means that I think highly of them and their products.
There are some comments about Diamond in post #2 here and the posts it links to that would be well worth reading. I would make sure that you are able to find out the information listed here so you can compare the quality of the materials and components to the durability guidelines here to make sure there are no lower quality materials or weak links in any mattress of theirs that you might wish to consider. If your budget is more restricted, then post #4 here and the posts it links to also include many of the better lower budget online options I’m aware of as well.
Phoenix