Hi DreamsComeTru4Me,
the first thing I would suggest is to read this article which can help you avoid most of the lowest quality and value choices when you are mattress shopping (such as most chain stores and major brands including the My Side mattresses).
A mattress is only as good as the materials that are in it and without knowing the specific quality specs of the layers in the MySide 3, there is no way to make meaningful comparisons with other mattresses or to know it’s real value. The odds are overwhelming however that you are paying too much for some low quality/density polyfoam that will be the weak link of the mattress and the first to soften and degrade. I would tend to avoid the My Side and Kingsdown unless you are able to obtain the type of information that will tell you it’s real quality and how durable it may be.
You can see some examples of the type of materials used in the My Side series in post #2 here (for the My Side series 4) and in post #13 here (For the My Side series 6). Their “bed match” system is basically a marketing tool that points to a specific Kingsdown mattress rather than really helps identify the type of mattress you would do best with regardless of brand. That’s a lot of money to pay for that much polyfoam and for dealing with a company that won’t tell you the quality of the materials in their mattress. You could do much better.
Post #10 here includes some steps you can take to help you “find” your best mattress. One of the most important steps is to find the local mattress manufacturers and better sleep shops in your area that have the knowledge and experience along with the quality value and service that can help make better choices before you start looking for mattresses at outlets that don’t give you anything more than marketing stories instead of meaningful information.
If you let me know the city or zip you live in I’d be happy to let you know of any I’m aware of that are within reasonable driving distance.
Phoenix