Hi dndcorzi,
The firmness of an innerspring depends on many factors including the coil gauge, height, number of turns, shape of the coil, number of coils, the type of coil, and the type of insulator and the foams that are above it. 12.5 gauge is certainly firmer than higher gauge coils but this is only one of many factors that affect the firmness of a mattress.
The density of a foam has nothing to do with its firmness and any density of foam can be made in a wide range if firmness levels. In a two sided mattress that is tufted … 1.5 lb polyfoam will be fine in terms of quality and durability.
I don’t know where they purchased their mattress (they didn’t say) or if they purchased from a factory direct manufacturer or a retailer but the posts I linked (for Nashville, Chattanooga, Knoxville, Evansville, and Birmingham) include all the factory direct manufacturers I’m aware of in the general area.
Other lists in a slightly wider area would be for Memphis here and for Louisville here.
Phoenix