UFX+/II was already an improvement over the UFX, see my blog: https://www.tonstudio-forum.de/blog/Entry/68-RME-UFX/
UFX III is again an improvement over UFX+/II.
The question is whether you need the improvements.
A few points, what UFX III delivers:
https://forum.rme-audio.de/viewtopic.ph … 11#p199511
See also the link to the comparison Excel in my blog.
I, personally, would sell UFX for a good price now as long as you get still a good price for it and invest into UFX III.
But it's not a real "must", it depends on whether you have the budget, whether you also want to have benefits from MADI in terms of expandability.
BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub14