What is your budget?
What kinds of games do you play.
Fast action games will benefit most from a graphics upgrade.
CPU limited games such as sims, mmo and strategy games not so much.
Try this simple test to assess how much benefit you would get from a stronger card:
Run YOUR games, but lower your resolution and eye candy.
This makes the graphics card loaf a bit.
If your FPS increases, it indicates that your cpu is strong enough to drive a better graphics configuration.
If your FPS stays the same, you are likely more cpu limited.
Your 600w psu will be the limiter on how strong an upgrade you can use.
Your psu is not the highest quality, so I would not push it. There are many cards that do not need more power than what you are now using.
Here is a handy chart:
http://www.realhardtechx.com/index_archivos/Page362.htm
Here is Tom's gpu hierarchy chart:
https://www.tomshardware.com/reviews/gpu-hierarchy,4388.html
Pick a upgrade that is significant or you may be disappointed if you do not see significant results.
I might think that one of the GTX1660 super/ti cards would be reasonable.