Had a Marcus from IKEA for years, switched out to a Herman Miller Embody and I can sit in it for hours without any butt or back pain.
I do wish I had a headrest on the Embody but its not the end of the world.
The HM range is expensive but with the 12 year warranty they're well worth the cost compared to cheap ones you'll likely replace.
I believe Atlas Headrests makes one for the embody. The one they have for the Aeron is a really nice match for that chair (colors, design and material)