Hi,
Can you give me more details of the system please.
Is it a thinkcentre m (whatever)
There are upgrade paths available which will eek you another couple of years out of it.
Most pertinent question is what do you want to do with it?
If it's gaming you'll need a discrete GPU of some description, and with it being SFF it's likely to need a half height.
Your CPU is a 35 Watt device, there are i7/Xeon's in the 45 Watt range but without details of the variant you have it's difficult to say if it will either work and/or have sufficient cooling.
Definitely invest in an SSD, the ar$e has fallen out of the solid state memory currently, so 500Gb/1Tb SATA drives are cheap as chips. As your processor is 2013+ vintage and NVME was released as a technology in 2012 this might be another option but impossible to tell without more information on the system.
I might have parts that can give you an uplift, let me know the model number and i'll see what I've got kicking around CPU wise.
Cheers
Lee