There's a couple of good "best of" mattress comparisons, and there's always the old backstop Consumer Reports. I joined on a discount subscription and they had a big mattress comparison report early in 2020.
Great timing since I HATED our Stearns & Foster mattress. Made an effort to buy local long ago and have tried two S&F mattresses - one pillowtop, one regular. We have a chest bed so no need for a box spring. I loathed both and unfortunately, they are an expensive purchase. I'm sure I'm not the only one who suffers with an unhappy purchase because it cost so much, you feel like you need to keep it long enough to get your money's worth out of it, LOL!
I liked the CR report as it tested for side sleepers (my spouse) and edge support (me), as well as longevity. This time I had a budget - we are flirting with the idea of downsizing and may not have room for a CA king bed in the future.
Plus, the reality is mattress life is considered to be 8-10 years! So I didn't want to spend more than $1500 - and preferably much less. Did you know that after 10 years, half the weight of a mattress is the dust that's accumulated inside? (So you're not getting weaker with age, that mattress is actually getting heavier!)
Next you have to decide what kind of mattress you want. Innerspring? Hybrid? Memory foam? Latex? All have advantages/disadvantages.
I wanted a firm/extra-firm mattress as I intended to purchase a mattress pad. I checked out the CR mattresses I'd noted. As luck would have it, after half an hour chasing down other mattresses (also reading the user reviews on the websites), I happened on a CR well-rated model that was on sale from a local chain.
It was a good price. It's a Beautyrest BRS900, extra firm, just shy of 15" tall. Delivery and install inside was free, only a modest charge $10, state mandated, for disposal and free takeaway of the old mattress. The latter was a big deal for us - a CA king mattress is HUGE and really heavy!
One issue with the mail-order mattress sites was that not all of them took away the old mattress, and the ones who did charged for it. Getting the takeaway for free saved between $35-50 from other companies.
I went on Amazon for the mattress pad. Was tempted by the one that somebody on Senior Forums recommended from Wal-Mart, but then I found a 3" latex foam pad at a slightly lower price. Latex is the type I prefer, but it is the most expensive mattress. As a pad it's a little more reasonable!
FYI latex tends to be "firm" - and very, very heavy. This was another consideration: if you rotate your mattress by yourself, a larger size latex mattress is REALLY heavy. Even as a 3" pad, this latex pad weighs almost as much as the much taller hybrid Beautyrest! Polyurethane foam pads are more medium-firm to soft in comparison, and very light - one person can easily handle even Queen or King sized.
Note this combo makes for a very tall mattress. I have bought extra-deep fitted sheets ever since we first purchased the first Stearns & Foster - that mattress was a whopping 21" thick!
Even with the cost of the pad and pad cover added, we spent less than half the cost of the S&F mattresses (I figured I can always buy another pad).
I sleep much better now. We'll see how long this pairing lasts, but only time will tell. HTH.