Hi eml298,
All of the vendors you have mentioned would be high quality choices IMO but you also have the option of local choices where you could actually test the mattress for your needs and preferences in person and avoid any of the risk of an online purchase. While this is not always possible because there are some areas of the country which don’t have good local choices … in Portland you do have some good options available including one of the members of this site.
They are listed in post #2 here.
There are too many variables to use a “formula” or what I call “theory at a distance” for figuring out the best mattress layering based on body weight, sleeping positions or other specs without a longer and more detailed conversation with the manufacturer or retailer of a mattress. They know every detail of the options and components of the mattresses they make or sell (not just the ILD of the layers) and have the benefit of a large database of customers that can act as a reference point and can also take any local testing you have done into consideration to help you decide which of the specific mattresses that they make or sell has the best odds of meeting your needs and preferences.
There are some guidelines that can help you understand the effects of different types of mattress construction and layering along with some height and weight guidelines and some sleeping position guidelines which can help you to ask better questions and better understand some of the “theory” behind different choices but specific “online” recommendations or suggestions are always more accurate on a phone call with the manufacturer or retailer of the mattress or through personal local testing where your body can tell you what works best for you.
Regardless of whether you choose to go in an online or local direction for an actual purchase … local testing can be very helpful as a guideline and either way have some very good choices available to you.
Phoenix