Try Hardox 400.
No need to tutor me, I was going to take the time to reply much the way you did.Please review the Young's modulus given for the three materials here:
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More generally for the collective, every steel, no matter what it trade name it hides under, has a stiffness so near 200 000 N/mm^2 it makes no significant difference.
If you need to make a steel structure stiffer, you have to change its geometry, and hence its second moment of area.
You can use a material with a higher yield strength, which means it can withstand a higher load before it deforms permanently, but that is not increased stiffness.
...I was going to take the time to reply much the way you did.
I've given up trying to explain, I now send them to read to Ohmer Blodgett's books.They are difficult concepts and what we say in everyday life (ordinary language) is sometimes at odds with the way the words are used in an engineering setting.
Sometimes it is needed to put people straight in a kind and informative way. If not, some of the suggestions they receive might not actually solve the problem they have.
I wonder if it is a flat surface (like a truck bed) if reducing the span of the existing plate might be a possibility. Or put dual wheels on whatever rolls over it to spread the load.