Hi Lilster530,
It sounds like it’s time to look for a new mattress and the first place I would start your research is the mattress shopping tutorial here which includes all the basic information, steps, and guidelines that you will need to make the best possible choice … and more importantly know how and why to avoid the worst ones.
As you can see in the guidelines here … I would avoid the major brands and the chain stores that tend to focus on them along with any other mattresses that use lower quality/density and less durable materials or unknown quality/density materials in their design.
There is more about the most important parts of the “value” of a mattress purchase in post #13 here that can help you make more meaningful comparisons between mattresses but all the mattresses you mentioned use lower quality and less durable materials than I would be comfortable considering and I would suggest avoiding them (or any mattress where you aren’t able to find out the information listed here)
It’s just marketing “stuff” using proprietary names that they have made up for their materials and isn’t particularly meaningful or provide any specific information that you would need to make an informed decision.
A foundation or bunkie board will need a flat and level support surface underneath it so they are evenly supported and won’t sag over time so if you wanted to keep the same support surface you would need to find out the reason that your bedframe is sloping and repair it.
Most mattresses don’t come with a box spring any more so you will almost always only see foundations. Box springs have springs inside them and flex under a mattress and foundations don’t have springs inside them and provide a flat and rigid support system that has little to no flex under the mattress. There is more about the types of support systems that are suitable for different types of mattresses in the foundation post here but as long as a foundation or support system meets the warranty criteria of the manufacturer then it would normally be fine. Some manufacturers (mostly online) don’t have a “dedicated” foundation that they sell for their mattresses and in some cases a particular foundation that goes with a mattress may not be particularly good quality (even though they meet their warranty criteria) in which case I would choose an alternative foundation that provides better support for the mattress. The height of the support system doesn’t make any difference and is strictly a preference (and some platform beds don’t need a foundation at all and can be used directly under a mattress) as long as it provides suitable support for the mattress.
You are the only one that can feel what you feel on a mattress and there are too many unknowns, variables, and personal preferences involved for anyone to be able to predict or make a specific suggestion about which mattress would be the best “match” for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) based on specs (either yours or a mattress) or “theory at a distance” that can possibly be more accurate than your own personal testing or sleeping experience (see mattress firmness/comfort levels in post #2 here).
I can certainly help with “how” to choose, help you narrow things down considerably by eliminating the worst options, act as a fact check, or answer any specific question you may have but if you are looking at major brands and chain stores I would “reset” how you are looking for a mattress completely and follow the steps in the tutorial one at a time which will give you the best possible chance of making the most suitable, the most durable, and the “best value” choice.
When you reach step 3 in the tutorial if you let me know your city or zip code then I’d be happy to let you know about the better options or possibilities I’m aware of in your area.
Phoenix