SetsulDepends a lot on what you're going to use it for.
If it's still good enough for whatever you're doing I wouldn't upgrade at all.
You should be able to reuse the case and PSU, maybe the RAM, but I'm not sure what would need that much CPU power and only 6GB of RAM. You might simply run out of slots if you want to keep those 6 DIMMs and need more RAM.
What programs are you going to use?
Im planning using it for mostly gaming/streaming and probably would do some video/image editing but not that much i think.