Dell Inspiron 580 CPU upgrade

Hello. I have an Inspiron 580 with a i5 750 CPU. I've been upgrading everything else for this decade (2 SSD disks, a 4K 60Hz graphic card, another 8GB RAM chip...). The only room for improvement is, I thing the CPU. I do not know if it's worth changing it or buying a new desktop (and tranfering the SSD disck, the 8GB RAM, maybe the 86€ 4K graphic card).

In case it is worth -and possible- changing the CPU... which models would work?

Thank you.