Hi iankh,
Welcome to the Mattress Forum! 
I’ll do my best to address some of your questions here. I’m glad that you’re not expecting anyone here to “choose” a mattress for you, as that’s not something that’s possible via an online forum because of the wide array of personal preferences and individual characteristics involved. Instead, the focus of the site is more on the “how” to choose. I’ll do my best to help in that manner.
First things first. If you haven’t already, please read the mattress shopping tutorial here, as it will provide (in as much detail as you desire) all of the steps necessary to make an educated mattress choice, as well as some of the common pitfalls to avoid.
About those pitfalls…
You may have already seen my comments about the Consumer Reports mattress ratings and recommendations in post #2 here and in this topic. While they may be a good source of information about more “objective” purchases, I would consider them to be an unreliable source of information or guidance about purchasing a mattress and their “ratings” are somewhat nonsensical and meaningless. My thoughts are also shared by most of the more knowledgeable people in the industry (see post #5 here for an example). I would avoid using them as a guide for making a mattress purchase.
I’m not going to go through the list of mattresses you mentioned, as much of what you mentioned is based upon ratings or Consumer Reports, which are both poor ways to select a mattress that is appropriate for your personal needs, although Sleep On Latex is a site member here, which does think that I think highly of their products and advice.
You seem to be in the Los Angeles area, and I think that you would be well served by visiting a local retailer and testing our some quality mattresses in person The good news is that you have quite a few good options in your area. Subject to first confirming that any retailer or manufacturer on the list that you wish to visit is completely transparent (see this article) and to making sure that any mattress you are considering meets the quality/value guidelines here … the better options or possibilities I’m aware of in and around Los Angeles are listed here.
While nothing has a 100% success rate, with a local purchase for the majority of people, careful testing using the guidelines in the tutorial rather than just testing for the more subjective “comfort” of a mattress (which often won’t predict how well you will sleep on a mattress or how it will “feel” when you sleep on it at home) and some good guidance from a knowledgeable and experienced retailer or manufacturer will usually result in a mattress choice that is well inside a suitable comfort/support range and will generally be “close enough” so that if any fine tuning is necessary it would be relatively minor and involve different mattress pads, sheets, mattress protectors, or perhaps even a topper if a mattress is too firm (see post #4 here and post #10 here).
One of the advantages of trying mattresses locally is that you can try many different types and styles and combinations of materials and components and firmness levels and compare them to each other in “real time” based on your actual experience rather than just “theory” instead of trying one online mattress at a time and not knowing how it compares to the other mattresses that you could have tried or purchased instead.
Some good local testing will also give you a much better sense of the many different types of materials and components that are used in mattresses and some reference points about the types of mattresses (see this article) and general firmness levels you tend to prefer which can help you narrow down your choices regardless of whether you end up purchasing locally or online. All of this will be more helpful and reliable than any “review” or ranking.
You will need to reinforce your slat network, by adding legs down to the floor or reinforcing these slats as T-slatsaftermarket metal slat system like this. Even your 22-year-old sleet set should have had this level of support. You can also remove the slats and add an if you desire.
Back then you would have most likely had the Simmons 4-fold torsion modular system that flexed a bit under your mattress. Today, most manufacturers are using versions of rigid foundations (discussed in the foundation thread here in more detail). If you end up purchasing something locally, finding the appropriate foundation shouldn’t be an issue. If you purchase a mattress alone, either locally or online, there are a myriad of online sources for appropriate foundations in the aforementioned foundation thread.
Overall, I would take a bit of time and read through the mattress shopping tutorial, and then find a few knowledgeable local retailers who can help guide you through the process of selecting a product that best suits your needs.
Phoenix