Hi drhoda,
My reply in post #2 here would be the same as my reply to you and I would avoid all the major brands completely (including Serta).
There is more information in post #9 here about the different ways that one mattress can “match” or “approximate” another one. Every layer and component in a mattress (including the cover and any quilting materials) will affect the feel and performance of every other layer and component and the mattress “as a whole” so unless you are able to find another mattress that uses exactly the same type of materials, components, cover, layer thicknesses, layer firmnesses, and overall design (which would be very unlikely) then there really isn’t a way to match one mattress to another one in terms of “comfort”, firmness, and PPP (Posture and alignment, Pressure relief, and your own Personal preferences) based on the specifications of the mattresses (even assuming that you can find out all the specifications you would need for both mattresses you are comparing).
Mattress manufacturers generally try to differentiate their mattress from the mattresses made by other manufacturers and don’t normally try to “match” another mattress that is made by a different manufacturer so unless a manufacturer specifically says in their description of a mattress that one of their mattresses in the same general category is specifically designed to “match” or “approximate” another one in terms of firmness or “feel” and PPP and/or they are very familiar with both mattresses and can provide reliable guidance about how they compare based on the “averages” of a larger group of people that have compared them (different people may have very different opinions about how two mattresses compare) … the only reliable way to know for certain how two mattresses would compare for you in terms of how they “feel” or in terms of firmness or PPP would be based on your own careful testing or actual sleeping experience on both of them.
The better options or possibilities I’m aware of in the Springdale/Fayetteville/Rogers area (subject to making sure that any mattress you are considering meets the quality/value guidelines here) are listed in post #4 here.
Phoenix