Hi sleepsuffering,
I would be very cautious about purchasing this mattress or any mattress where you aren’t able to find out the quality and durability of the materials and components inside it no matter how comfortable it may be in a showroom (see this article).
Outside of PPP which is all about how well you will sleep on a mattress … in terms of durability a mattress is only as good as its construction and the quality of the materials inside it regardless of the name of the manufacturer on the label because the quality and durability of the materials will determine how long you will sleep well on a mattress before it loses the comfort and support that was the reason that you purchased it and you would need to buy a new mattress (and the loss of comfort and support isn’t covered by a warranty),
If there are either lower quality materials or unknown materials in a mattress then it would be a very risky purchase and I would avoid it (see the guidelines here),
There are some links to lists of some of the better online choices I’m aware in the tutorial post (in the optional online step) that would be well worth considering if you are comfortable with an online purchase.
There are also no “standardized” definitions or consensus of opinions for firmness ratings and different manufacturers can rate their mattresses very differently than others so a mattress that one manufacturer rates as being a specific firmness could be rated very differently by another manufacturer. Different people can also have very different perceptions of firmness and softness compared to others as well and a mattress that is firm for one can feel like “medium” for someone else or even “soft” for someone else (or vice versa) depending on their body type, sleeping style, physiology, their frame of reference based on what they are used to, and their individual sensitivity and perceptions. This is all relative and very subjective and is as much an art as a science. There are also different types of firmness and softness that different people may be sensitive to that can affect how they “rate” a mattress as well (see post #15 here).
I would also be very cautious about using other people’s experiences or reviews on a mattress (either positive or negative) as a reliable source of information or guidance about how you will feel on the same mattress or how suitable or how durable a mattress may be for you and in many cases they can be more misleading than helpful because a mattress that would be a perfect choice for one person may be completely unsuitable for someone else to sleep on (see post #13 here).
I would make sure that you’ve read post #2 here which I linked in a previous reply which has more about the different ways to choose a suitable mattress that is the best “match” for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) that can help you assess and minimize the risks of making a choice that doesn’t turn out as well as you hoped for that are involved in each of them but the only way to know for certain how a mattress will feel for you or whether it’s a good “match” for you in terms of PPP will be based on your own careful testing (hopefully using the testing guidelines in the tutorial post) or your own personal experience.
Phoenix