Hi WildStringdom,
The first place I would start is post #1 here which has the basic information, steps, and guidelines you will need to make the best possible choices … and perhaps most importantly eliminate the worst ones. Unfortunately either the places you have tested mattresses or the specific major brand mattresses you tried don’t provide the information you would need to make any kind of meaningful comparisons or assessments so spending time there is mostly wasted unless you intend to purchase one of the mattresses you tried based on the showroom feel alone and as you can see in an earlier reply today here I certainly wouldn’t recommend this.
Unfortunately there is no way to make any kind of meaningful quality or value assessment without knowing what is inside them so you can make meaningful comparisons with other mattresses available to you.
I don’t keep a list of specific mattresses at any store or manufacturer (outside of what is on their website or some general information about the brands or types of mattresses they carry based on phone calls I have made) which would be an impossible job. They are often changing as well so even if someone was able to put such a list together it would be long out of date by the time it was complete. The best way I know is to follow the steps in the first post I linked one at a time. One of the most important parts is to talk with the retailers or manufacturers you are considering on the phone and let them know your criteria both in terms of budget and the types of mattress you are interested in testing (if their website isn’t up to date) and to make sure they are able and willing to disclose the information you need before you even step out of the house to visit them. This will give you a much more clear idea of who has mattresses on their floor that you are interested in testing in your budget range and the type of knowledge and service you can expect if you go there and then you can narrow down which ones to visit much more effectively.
You should certainly be able to find a mattress in your budget range that will last you 5 - 8 years but your initial phone research from home and who you deal with can be just as important a part of your success as the mattresses you test.
Phoenix