Hi sebm,
You’ve probably seen this but just in case you haven’t … the better possibilities in the DC area are listed in post #2 here.
The Renewal refined is really a memory foam mattress (the top 4.75" are memory foam and the latex is only a thin transition layer in between the memory foam and the support core) but regardless of this I certainly wouldn’t consider a major brand like Serta or the iComfort line anyway because of their poor value (see the first guideline here).
I think Healthy Back is certainly one of the better retailers in the area and are generally very knowledgeable and open about the mattresses they sell. The Pure Latex Bliss mattresses they sell are usually “better than average” value but not in the “best value” range but their current pricing has been reduced and I would currently put them in the “good value” range. The Essence is their 10" model which would be similar to the old version of the PLB nature (see the specs here) except that the top layer uses Celsion which the old versions didn’t and in this way would be similar to the new PLB models. They should be able to provide you more specific details.
Regardless of the specific construction though … your personal testing would tell you much more about how suitable the mattress was for you in terms of PPP (Pressure relief, Posture and alignment, and your Personal preferences) much more than how well it may have met someone else’s comfort and support needs. In terms of value … their current prices are good value IMO for any mattress that is made of 10" of blended Talalay latex regardless of who manufactured it especially considering that you are able to test it in person.
Hope this helps
Phoenix