If you want something firmer from Casper, all of its other mattresses are firmer than the Dream Max Hybrid. The base model Dream Hybrid is a medium, and the Casper One is the firmest option ...
Memory foam beds usually perform best in this category and the Casper One uses a layer of memory foam along with its foam support base, so I expected it to be good, but maybe not quite this good.
The Kin by Tuft & Needle, the Casper Element ... bundles (and Amerisleep just so happens to make our favorite adjustable bed base). The Aviya is our favorite hybrid mattress.