Welcome to the forums my friend!
It's not a huge upgrade, but it's an upgrade useful enough that likely won't cause a big issue on the CPU. But this depends on the application.
It also depends on what games you are playing? (Assuming you are gaming).
Also what PSU make and model?
You can see FPS comparisons here:
https://www.game-debate.com/gpu/ind...1660-vs-geforce-gtx-970-zotac-4gb-edition-sli
As you'll see it is a good upgrade, not huge however, and in some applications not that significant.
So I will return to my usual "is it worth it" response to everything - it's worth it if the value of the card is worth the FPS you'll get to YOU