Hi deryk,
A memory foam topper on top of a mattress may feel different than the same memory foam layer inside a mattress that uses different layers and components because every layer and component in a sleeping system can affect the feel and performance of every other layer above and below it.
I would also keep in mind that there are many types of memory foams that can have very different properties (see post #9 here and post #8 here) so a single topper on a particular mattress wouldn’t be representative of all the memory foam mattresses that are available.
If it’s possible you may be better off spending some time on a range of different memory foam mattresses (I would spend about 15 - 20 minutes on each of them so the memory foam has time to warm up) so you have a better sense of the range of memory foam mattresses that are available which may give you a better idea of how you like memory foam in general or whether you tend to prefer some types of memory foam over others (such as more or less temperature sensitive, firmer or softer, thinner or thicker layers or memory foam, or faster response vs slower response memory foams etc).
Of course the advantage of trying a topper is that you would have the chance to sleep on it overnight which would tell you more about that specific memory foam than just 20 minute “test runs” but again any specific topper wouldn’t be representative of the whole category of memory foams so you may find that you don’t like a specific topper but may like other types of memory foam or other memory foam mattress designs (or vice versa).
You are certainly out of the way and unfortunately the closest forum list to you is the Central Montana list in post #5 here but none of them are very close to you…
I did a quick check to see if there was anything that was closer to you and there certainly aren’t a lot of choices. While I didn’t have the chance to talk with any of them … based on the information on their websites (which isn’t always accurate) some of the local options that may be worth considering and the manufacturers they carry that I would focus on that may be more transparent about the materials in their mattresses (and subject to the quality/value guidelines here) include …
http://mossholders.com/ Sheridan, WY. They carry Northwest Bedding which may include some better quality mattresses. They also carry Serta which I would avoid completely as a purchase but would give you a chance to test some memory foam mattresses.
http://www.carrollsfurniture.com/ Sheriday, WY. They carry Natura mattresses which make some good quality latex and latex hybrid mattresses. They also appear to be knowledgeable about foam specs.
Time permitting I’ll try to make some calls tomorrow to see if there are any others that may be worth adding to the list.
Phoenix