Hi GrumpyOldPerson and welcome to the Mattress Underground 
New here, so forgive me if I’m misusing the site. DH & I are lightweight, moving from a age 20+ memory foam from Joanne’s Bed & Back shop. Want memory foam–we like a “dead” bed. Have used a topper for a few years as bed is slowly sagging middle.
Sorry to hear of the sagging in your current mattress- 20 years is a good run for memory foam! You have come to the right place… you mention you have to ‘do some more homework’ - you might want to include reading our [Mattress Shopping Tutorial] to see how to assess a good mattress retailer, and the [Mattress Durability Guidelines] to see how specific materials compare to the [Mattress Specifications You Need To Know].
Any mattress that you decide on will be based on your Stats (height, BMI, sleeping position(s) and any underlying health concerns, and your PPP (Posture and alignment, Pressure relief, and Personal preferences). You don’t say what other layers and materials are in your current mattress, like polyfoam or innersprings, but many consumers enjoy memory foam for the ‘dead’ feeling you mention- the lack of motion transfer. You say you are both lighter sized, so I would keep in my that excessive amounts of lower grade foam can breakdown prematurely leaving ‘divots’ which can affect alignment as well as cause muscle and joint pain; you should make sure any foam in a potential mattress has no more than an inch or so of lower grade foams (for memory foam no lower than 4 lbs/cuft for normal range weights) and if polyfoam is used, with at least 1.8 lbs/cuft density, just to ensure you have support.
Now, would someone recommend a good local (retail) source here in Reno, NV to work with? We probably would be happy to replace our old bed with one similar, but really need to do some test lying down in addition to some more homework on specific materials/density, etc.
Unfortunately, with all the business turnover in the last few years, we aren’t able to provide geographic listings of retailers and manufacturers.@Phoenix has some suggestions for Reno showrooms in This Post that might be of use, though it’s from 2017.
While you are correct in wanting to test in person, as that is the best way to see how a mattress feels, most of the Trusted Members of the site do ship across the U.S., and are experienced in matching sleepers with their ideal sleeping solution, with good customer service, quality material and construction, and generous return and exchange policies, if you do decide to explore online options. Also, MattressFirm in Reno carries Trusted Member GhostBed who offer several memory foam and hybrid memory foam mattresses that may interest you. Hopefully, other forum members in the Reno area can comment on their experiences with local showrooms as well. If you find a few mattresses you are interested in we can possibly comment on how they may work with your Stats and PPP. Here’s hoping you find the ideal mattress for another 20 years!
~ Basilio