Hi tarpon21,
If you haven’t already, you’ll want to read the post about how to select the best mattress for yourself. Phoenix has done a wonderful job explaining how to evaluate a mattress for its suitability for yourself, and understand the quality of the materials. It sounds like you may have done some of this, but in case not…
https://forum.mattressunderground.com/t/how-to-look-for-and-find-the-best-mattress-for-you-read-first
As to pricing, and seeking member feedback, you’ll need to say what size of bed?
The one thing I’ll note with memory foam is that different manufacturer memory foam can feel different, even if it’s the same density. Memory foam making is a proprietary process, with the formulation and foam making being different for each company.
I believe there is a novosbed representative that posts in the forum from time to time.
As to sag, in addition to buying high quality/durability materials (which it sounds like you are already doing), you’d want to ensure you have a suitable foundation to support the mattress. You could certainly cause premature sag with a high quality mattress on a poor / unsupportive foundation.