Hi mattvs86,
You’re welcome. 
[quote]Each layer is 3". My favorite configuration.
Top: soft/talalay
Mid: med/dunlop
Bot: firm/dunlop
I also liked the ability to switch layers. I was able to put the bottom firm layer in the middle, medium on the bottom, and that created a little more support if I would like.
[/quote]
Many people prefer component mattresses and the ability to customize your comfort and replace layers over time. Savvy Rest is one of the mattresses in this category.
While Savvy Rest certainly uses high quality components in their products, they are in a price range that many consumers might find a bit high and they may consider some other options from brands that carry similar componentry and prices ranges that may be more affordable. Many of the members of this site (post #21 here) offer options similar to what you mentioned, and a phone call with them would be your best bet to gather information on making a choice that approximates the item you saw in Minneapolis. Post #2 here and this topic have more about the pros and cons of a local vs an online purchase.
An organic designation doesn’t necessarily reflect or impart a comment upon the durability of a product. All latex foam you encounter, (SBR, NR, SBR/NR) will be a very high quality and durable material.
There is also more about the different types and blends of latex in post #6 here but all of the latex you are likely to encounter (either Dunlop or Talalay that is made with either natural or synthetic rubber or a blend of both) will have a reliable safety certification such as Oeko-Tex, Eco-Institut, or Greenguard Gold (see post #2 here) and based on actual testing I would consider any type or blend of latex to be a very “safe” material in terms of harmful substances and VOC’s. I would also consider all of these types of latex to be very durable and higher-quality products. Without getting down the rabbit hole, there are some small differences for different blends and their properties, but nothing that in my personal opinion would rate too highly on a list of items to consider.
Talalay Global has listed that their testing shows that their blended Talalay is more durable than their natural. Radium’s Vita Talalay (what you were looking at with the Savvy Rest) tests out to be superior to their blended. Again, these differences are small and they are all high quality materials.
Regarding how having synthetic in the latex will change the feel, it’s not a simple equation that having a blend versus a natural will result in “x percentage” of change in a particular level of comfort. There is no one algorithm that can predict such a thing. And remember that a single sheet of foam is part of the entire mattress system and is influenced by everything in the mattress, including the cover. Different blends from different companies all have slightly different feels. At a comparable ILD, most of these differences in feel are subtle, and are of course relative to your own opinion and PPP, because the number one rule is that only you can feel what you feel.
Rearranging your mattress in this manner would be more of an issue in fine-tuning your comfort preference. While not a “normal” configuration, I wouldn’t hesitate to do this if this is what you personally preferred for any fear of shortening the comfort life of your mattress. The layers closer to your body have a greater impact upon your comfort and will tend to “wear” faster, but with the materials you’re choosing durability wouldn’t be a concern.
Again, I can’t tell what “you: will feel, but in general there certainly would be a difference in configuration (assuming you’re using the same foam) by replacing the bottom 3” firm layer with a 3" medium layer. You might notice a bit of a softer feel in the “deep support”. If you want to learn a bit more, there is also more about primary or “deep” support and secondary or “surface” support and their relationship to firmness and pressure relief and the “roles” of different layers in a mattress in post #2 here and in post #4 here that may also be helpful in clarifying the difference between “support” and “pressure relief” and “feel” that may be useful as well.
As you are probably aware, SleepEZ and FoamSweetFoam are members of this site which means that I think very highly of them and that I believe that they compete well with the best in the industry in terms of their quality, value, service, knowledge, and transparency. They are extremely knowledgeable about latex and different configurations, and I would not hesitate to recommend them for your consideration.
When you can’t test a mattress in person then the most reliable source of guidance is always a more detailed phone conversation with a knowledgeable and experienced retailer or manufacturer that has your best interests at heart and who can help “talk you through” the specifics of their mattresses and the properties and “feel” of the materials they are using (fast or slow response, resilience, firmness etc.) and the options they have available that may be the best “match” for you based on the information you provide them (like the Serenity model you tried), any local testing you have done or mattresses you have slept on and liked or other mattresses you are considering that they are familiar with, and the “averages” of other customers that are similar to you. They will know more about “matching” their specific mattress designs, options, and firmness levels to different body types, sleeping positions, and preferences (or to other mattresses that they are familiar with) than anyone else.
Good luck!
Phoenix