Hi kysoreback,
Unfortunately … without the specifics of the layering in each I can’t really help you make any meaningful assessments or comparisons and I don’t know the layering of either the Williamsport or the Sensation (and a quick online search didn’t provide any further information of either).
I can tell you that the Pamper isn’t a latex hybrid (which is several inches of latex over a different type of support core usually an innerspring or polyfoam) but an all latex mattress which of course means it uses more costly materials (latex is a higher cost material than either innersprings or polyfoam). It would also be helpful to know if this was the old Pamper (with the white cover and an inch of latex in the comfort layer) or the new Pamper (with 2" of latex in the comfort layer and a blue cover).
Post #2 here talks about the pros and cons of a latex hybrid vs an all latex mattress in general terms.
I would also need to know the layering of the two hybrids you are looking at to compare them to the Ultimate Dreams but it does have exceptional value and it would be unlikely that you would find anything locally that would be in the same value range at least in terms of materials. Of course … a local purchase is also less risky because you can test it in person to make sure it suits your needs and preferences which adds to local value a well. I normally use a 20% difference between local and online as being “equivalent value” but each person may have a different risk tolerance and use a different number. The Ultimate Dreams also has a 3" comfort layer and 1.5" of softer quilting so given your experience I would choose a firmer layer than average for your height and weight because the quilting will add to the softness of the layer compared to just the latex ILD alone. They can also make a tighter quilting pattern (making it a bit firmer) which I would probably suggest as well if you go in this direction. Either way though … knowing the details of the Williamsport and Sensation would help you make a more appropriate choice.
It would be interesting to know the details of the material in the sofa sleeper but as you mentioned it does tend to point towards the need for a firmer support core and thinner comfort layers (like the Pamper) or at least firmer comfort layers if they were thicker. You may also do well with a single 6" layer in the right firmness (probably in the range of 'medium") without a comfort layer at all … particularly if it was latex which is very conforming and point elastic and can be soft with initial compression but then gets firmer more quickly than other types of foam with deeper compression.
This firmness preference is not uncommon with people who are lighter who are often at either end of the spectrum. They will often do well or prefer a softer than average comfort layer (because their lighter weight needs softer foam to sink in enough) or do well with a firmer than average surface (because their lighter weight and body shape isn’t as pressure prone and they tend to prefer the greater freedom of being more “on” the mattress instead of “in” the mattress). People who tend to “sprawl” will also often do well with firmer layers. My only caution would be your side sleeping which is a more pressure prone position and it would be interesting to know if you spent time on your side when you were on the sofabed.
A firmer preference would also make it more likely that your choices would come closer to matching your husband who is heavier (even though he can sleep on anything) and would normally need more firmness in both the comfort and support layers than you would … particularly with his stomach sleeping.
I wish I could be more specific but with the “gaps” in the information it’s not really possible.
Phoenix