Hi lingling008,
Thanks for including your personal stats . I’m sorry - I wish there was a magic solution that would apply to your situation and pre-existing issues, but as you surmised, it isn’t as cut-and-dry.
At your normal to light BMI and extra firm comfort/support needs due to your scoliosis with Harington rods a 13" thick mattress is a bit of overkill unless you like to have a thicker mattress. Because of your budget restraints, I’d recommend that you opt for a thinner mattress with better components.
Outside of PPP (which is the most important part of “value”), the next most important part of the value of a mattress purchase is durability which is all about how long you will sleep well on a mattress. The “weakest link” in a mattress in terms of durability is normally in the upper layers (the top 3" - 6" of the mattress) that are compressed more deeply when you sleep on it and not generally in the deeper support layers so the firmer bottom layers of a mattress will have more effect on feel and performance than they will on durability for most people.
While Beautyrest’s memory foam mattress you are looking at has a T1 Pocketed coil for support that is unlikely to be the weak link … the undisclosed density/quality of the comfort/transition layers above the coil may present issues in terms of durability and how long you will sleep well on this mattress. Regardless of the name of the manufacturer on the label or how a mattress feels in a showroom, before considering any mattress I’d begin by finding specific mattress quality indicators that you "can’t see or "feel (see mattress information you need to know) such as density and thickness of each of the layers ( in this case AirCool® Foam / Firm Comfort Foam / Beautyrest® Charcoal Memory Foam) so you can compare the quality of the materials and components to the https://mattressunderground.com/our-articles/mattress-durability-guidelines-how-long-will-a-mattress-last.html mattress durability guidelines here to make sure there are no lower quality materials or weak links that would be a cause for concern relative to the durability and useful life of a mattress before making any purchase
With your scoliosis condition, it becomes especially important to find the best balance between pressure relief and support/alignment (along the length of your spine) for your side sleeping position. Alignment/support is the most important thing that a mattress does for you, so you’ll always want to choose something that doesn’t allow for too much of an accentuation of your lateral curvatures when side sleeping. Generally, you’d want something with “just enough” surface plushness to assist with contouring for your shoulders and hips. I wouldn’t be able to tell you how much that would be, as there are so many variables involved, including your body type, level of sensitivity, and of course your back issues.
This said I think that you would be well served by all latex or hybrid-latex mattress. Latex is both very supportive and gives relief from pressure.
The key is to find someone who is willing to help and guide you and who will do more to educate you about the real differences between mattresses and how to find a mattress that “fits” your needs and preferences (regardless of brand) rather than focus on trying to sell you something that they carry (and that makes them the most possible profit) can be your best friend. The best of these are usually at local factory direct outlets and local sleep shops that carry smaller local or alternative brands (not major brands that are made locally). While there may be many good options in Vancouver BC some of the “tested and tried” manufacturers that I am aware of and are part of our Trusted members program would be able to guide you or offer you something unique that is suitable for you.
[indent] ~[url=https://en.memoryfoamcomfort.ca/main.html]MFC[/url]Canadian online retailer with a very good selection of latex mattresses and hybrids that would fit your budget range. They are one of our expert members with a 9URL= http://forum.mattressunderground.com/c/talk-to-the-experts/mfc]dedicated forum here[/url].[/indent]
~ Another system you may be specifically interested to see is CBH Wood’s “Tri-Slat” slat system consisting of latex on wooden slats in conjunction with the supportive latex strips, is placed on a solid wooden frame. This system allows for dynamic adjustments of the support/comfort functions of the bed due to body’s weight, shape, and various sleeping positions, thus promoting adequate spinal and joint alignment. The system’s design has the capacity to accommodate a wider range of individual sleeping positions and needs. Here is what one of CBH wood customers with complex medical conditions reports about the Balancer system
[indent]~ [url=https://dormio.ca/product-category/dormio-organic-mattresses/]Dormio[/url]Canadian Manufacturer specializing in organic/natural latex mattresses with options that fit all budget ranges.[/indent]
I hope some of this information brings a bit more clarity on what is best to focus on in your mattress research
Phoenix