Hi MrMattress,
Glad you found the info I provided helpful. Sherwood was recently purchased by Sealy; and while there’s no way to tell how that will affect the quality of the mattresses they provide going forward, their lack of transparency in material thickness, firmness and composition on their site makes it impossible to assess how the various comfort and support layers may work for consumers, and how they compare to the Mattress Specifications You Need To Know and the Mattress Durability Guidelines. I would avoid any mattress that does not provide this info as this can hide suboptimal types and densities of foam and construction ‘shortcuts’ - though either of the Sherwood Lumina mattresses you mention could work for you. Also, we have heard from other consumers that these are backordered and availability is difficult at the moment as you can read in post #22 here and the first post here.
As you and your wife are lower BMI sleepers, you should not concern yourself too much with additional support…any mattress, of quality, should provide adequate support for you from the Stats you provided - thanks for giving those!
As far as microcoils ‘holding up’…again, as you are both lighter, there should be no issue in prematurely wearing out a microcoil layer. You can see @Phoenix on microcoils here it comes down to your preferences - you should not ‘need’ a dual coil support layer, if you can dial in the correct firmness for your comfort layers that is not too soft nor too firm, as you do not like the feel of either extreme - that’s the missing piece of the puzzle.
In your case it might help, if possible, to try some various mattress types in a local retail store or showroom - all latex, latex hybrid, memory foam, memory or gel hybrid, etc - so you can make a short list of materials that feel comfortable for you and your wife; then you can focus on finding a good quality mattress with known densities and materials used in their construction. At the price point you mentioned, there are many great mattresses in that range…you may also want to consider looking at the offerings of our Trusted Members as they offer mattresses of all types, styles and firmnesses, and they have been vetted for quality, transparency, and excellent customer service. If any specific mattresses catch your eye we may be able to comment on how they might work with your specific needs and preferences. I wish you success on your search!
~ Basilio