Landon, some advice from another knife guy: don't get too obsessed over steels and HRC. Most people won't be able to tell the difference. There are tradeoffs with harder steels, too. S30V, and for a harder steel, M390, are great steels, without the tendency to chip or roll that high HRC steels can have. Not to say the difficulty to sharpen. There is no perfect steel; if you are going to use your knife for all sorts of cutting, S30V should be excellent.
If you can go up a step, I suggest M390. I have several knives with ZDP-189 HTed to 67 HRC. But honestly they cut just like my S35VN blades, as far as I can tell. Again, to the average guy, cutting cardboard, wood, and opening envelopes, you probably won't be able to tell the difference. In other words, don't sweat it. Perfection is the enemy of the good, as some wise person once said.