Purchasing a new mattress is an investment that you should have for many years. Of course you want it to be comfortable but it is important that it look good with your existing headboard. If your headboard is over twenty years old, the chances are pretty good that the thick mattresses will end up burying most of your headboard. That happened to a client of mine.
When her new mattress and box spring arrived you only saw the very top of the heardboard. The rest was buried. I suggested that she get a low profile box spring - which she did. That reduced the height of the box spring by several inches and you could see more of the headboard. The mattress was still substantially thicker than her old one but it was a vast improvement.