Honestly, I have done a complete 180 on the idea of buying an expensive mattress. I think you will be just fine buying a really firm mattress of a less expensive brand, and then spending $100 or so on a quality memory foam mattress topper. Get the new gel ones that don't get too hot, and get as think as you want. You won't even know what type of mattress you have underneath you.
About 10 years ago, my wife and I bought our first King size bed, and decided to go all out on the mattress. We shopped for quite a while, and wound up with a Stearns and Foster model that provided me the best sleep I have ever had.....for about 3 months. Eventually the mattress started to sag underneath me a bit (I'm 6'1", 210) and I felt like I was sleeping in a trench. We rotated the mattress, of course, and the trench started forming on that side as well. We couldn't flip the mattress, because mattress makers now rip us all off by making their mattresses one-sided. The trench was not even close to being deep enough to be a warranty issue, but it was deep enough that it was killing my back. So, maybe we had a bit of a "princess and the pea" issue, but I couldn't take it.
I bought a mattress topper, and that cured everything. Great rest, but I had to wonder why I needed a $2,000+ mattress and box spring set when the $100 topper was the key.
Fast forward a few years, I'm divorced, and setting up my new home. I pulled out a queen sized mattress I had owned since 1993, but which was in our guest bedroom for our marriage. Cheap-ish mattress, but I threw on a quality mattress topper and I love it. Better than the Stearns and Foster when it was brand new.
Oh, and you can get the mattress toppers for a good price at Costco or Sam's Club.