Any CPU/GPU combination from the past half a dozen years will be fine.  I am running a Ryzen 7 2700/RTX 3060 (12gb) system right now.

One thing to remember is that Opitx will use as many GPUs as you can throw at it. 12Gb RTX 3060s are pretty cheap, both new and used.

My current gameplan is a CPU/MB replacement next month - I picked up a Ryzen 7 5700x and next month I'll pick up an X470 motherboard, and a 2nd RTX 3060.