Hi dragons4Mama,
If the only issue with your futon is that it’s too firm and you just need some additional softness and pressure relief then it may be worth considering a topper instead of a whole new mattress. Post #2 here and the topper guidelines it links to has more information that can help you use your sleeping experience to choose the type, thickness, and firmness of a topper that has the best chance of success.
As you probably know from reading the site … I think very highly of Neal and Spindle and they are a member of this site which means that I believe they compete well with the best in the industry. The Natural Dunlop latex that they use in their mattresses is a higher quality (and much more costly) material than any of the layers in the Casper mattress and a component mattress also has the advantage of being able to rearrange or exchange the layers so you can “fine tune” the mattress after a purchase if you need to. They also have the advantage of being able to replace a single layer instead of the whole mattress if one of the layers softens or breaks down faster than the others (usually the top layer) or if your needs and preferences change over time. You are also very fortunate that you are close enough to test the mattress in person. A forum search on Spindle (you can just click the link) will bring up more information and feedback about them.
There is also more information about Casper in posts #2 and #5 here and in post #2 here and you can see some of thoughts about some of the “one size fits all” mattresses that are becoming more common in the market in post #2 here. A forum search on Casper (you can just click this) will bring up more information about them as well.
Phoenix