Hi Jaclync,
The better sources for mattress materials and components that I’m aware of are listed in post #4 here.
This would depend on which materials you are keeping, the types of materials you tend to prefer, and on what other layers you would be combining in the mix on top of the innerspring. There isn’t a “theory” that can predict which combination of materials would work best for you or that you would prefer outside of your own personal experience but I would base any additional choices on a careful assessment of how your mattress feels and performs with what you already have (or are keeping). Both Talalay and Dunlop are high quality materials but they are different from each other in terms of how they feel and perform and the choice between them would be a preference choice. There is more about the differences between them in post #7 here but the best way to know which one you would tend to prefer would be based on your own testing or personal experience.
All of the different types of material that you may prefer will have lower quality and less durable versions and higher quality and more durable versions and regardless of which materials or combination of materials you tend to prefer … I would make sure they were high quality and durable so that they don’t soften and break down prematurely because the weak link of most mattresses is the quality of the materials in the comfort layers.
Phoenix