Hum. Please update your forum profile, it says you use SU2020 on a radeon 64 
Are you running ventura or monterrey ? I’m gonna bet Ventura. Some people have really bad experiences with Ventura and SU 2022, at this point, the best course of action is to rollback to Monterrey, and in general, to NOT update the OS unless ALL your softwares says they are compatible. SU is not (yet) compatible with SU22. We’re expecting SU 23 any day now.
I run the same machine, (ok, 500gb not 256), no crashes, even on weird files. And I’m still on monterrey.
Now, if you REALLY want to change your gear, beware, you’ll be stuck with a new machine using Ventura that you won’t be able to rollback to monterrey, and chances are, you’ll still have issues with SU2022. My advice is to wait for SU23 to release before selling a kidney and changing your gear.
Now, to the main question at hand. Mac mini M2 Pro.
The M1 max is a M1. I mean, it’s still a 3,2 Ghz processor, more cores but same clock. And 3d softwares are using a single processor to work, no matter if you have 7, 8 or 19. M2 clocks at 3,5 Ghz.
Real question is, how much RAM do you want ? I reckon a 32 Gb mac mini will do really fine (when I see what I can do with a 16gb M1). But yeah, if you really want more, you’ll have to go studio.
thing is, at this point, consider a PC. For 2k+ €, you’ll get a solid machine with twin graphic cards (optimized for renderers like vray) that you’ll be able to upgrade later.
I realize it’s not the answer you seek, but you have a fine machine, most likely limited by the incompatible OS for now.
Macs are good, I like Macs, but PCs are cheaper and easier to optimize.
The fact that for a small bump of performance (between mini and studio) you have to sell a second organ is not worth it in my opinion. At this price, buy a second computer.