The best mattresses I've bought have been middle-of-the-road firm inner spring models from Serta and Seely, including a couple bought from Costco. Not expensive, delivered, great for about 8-10 years, repeat.
I've tried foam-type mattresses and never found them to be right for me, and they tend to feel hot to me as well. The WORST mattresses I've bought were higher-end ones from companies like Stearns and Foster that were very thick and heavy and included super-plush toppers. Within a year or so, the toppers started to sag and compress and the mattresses became unsupportive within a couple of years. Ugh.
That happened twice and decided to stick with conventional inner spring, non-super-plush "regular" firm mattresses thereafter and have been happy that way.