I went through the same thing recently. I treat this as a 15 year purchase, I'm not willing to throw something that big in the dump on a regular basis.
Buying something online without trying it first that you're married to for that long seems insane to me. Especially when all online mattress companies are largely born out of how to fit a mattress in a small shipping unit rather than how to make the best mattress.
Basically all the review sites online are scams. Everything "independently" top rated shows up as having issues 2 years in if you search reddit.
Sleep Country/Leons/The Brick are all pretty sleazy with massive markups and more and more low end garbage ending up on their floors. You can snag a Tempurpedic from one of those places on sale and you're probably doing pretty well.
I ended up going with
Black Sheep. They get great reviews from actual people on Reddit. They are manufactured in Calgary and made with all natural materials so you aren't spending 8 hours a day on something off-gassing carcinogens. They've only been around since 2011, so not quite the longevity track record I'd prefer, but I couldn't find anyone complaining about short term failures.