Hi Electricone65,
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 know how and why to avoid the worst ones.
Brand shopping can be among the most risky ways to choose a mattress because all manufacturers have access to the same or similar components and materials and most of the most heavily advertised and most commonly available brands that you would recognize are the ones I would avoid anyway (see the guidelines here) and many of the better manufacturers are smaller and are only available locally or regionally. The name of the manufacturer on the label also won’t tell you anything about whether a specific mattress is suitable for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) or whether there are any lower quality materials or weak links in the design. There is more about the risks of brand shopping in post #5 here and post #12 here).
I would focus much more on the types of mattresses and materials you tend to prefer and on using the information in the tutorial to find more knowledgeable retailers or factory direct manufacturers either locally or online that are completely transparent about the materials in their mattresses and that can provide you with the type of guidance that can help you make the best possible choice regardless of the name of the manufacturer on the label
Only the foam layers inside a mattress have an ILD … not the mattresses themselves (and a mattress usually has several layers with different ILD’s). 40 ILD is very firm and can work well as a support layer for some people but it would be much too firm for most people to sleep on directly if it was used as the comfort layer of a mattress.
Having said that … 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 or recommendation 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).
Pure Latex Bliss mattresses would be more than your budget in a king size (outside of possibly the Pamper which is their thinnest and firmest all latex mattress) but there may be other options in your area and if you let me know your city or zip code I’d be happy to let you know about the better options or possibilities I’m aware of that are close to you.
The tutorial includes a link to a list of the members here that sell mattresses online (in the optional online step) that compete well with the best in the industry in terms of their quality, value, service, and transparency and many of them also make latex and latex hybrid mattresses that use different types and blends of latex that have a range of different designs, options, features, return and exchange policies, and prices that that would be well worth considering and would be inside your budget range.
Phoenix