I would suggest you get the 2060 super instead, imo. Also, a gpu upgrade is always the best upgrade to make in your system to get more fps in games. And yes you will get a substantial amount more fps!
WITH THAT SAID... the cpu though. I had the 2600 with my 2060 super. And the CPU struggled to keep up with what the 2060 super was capable of.
If your a competative gamer and turn most games to lower graphics to get more fps, is where you might run into an issue with the 2600. Still some issues at higher settings as well, but moreso when they are lower settings. The lower your settings and resolution, the more the cpu works to render the game. SO by turning down your graphics your working the CPU harder and depending on how well the CPU is, in those cases, will determine your gaming experience. The 2600 is good for 60-100fps gaming. But when paired with a 2060 super the 2600 struggled to maintain a higher fps on the low end. They call this the 1% lows.
In Apex Legends I was getting 200fps in most areas, but was dropping down to as low as 100fps in heavy areas, especially if in a gunfight. So if your a competative gamer and play games at lower graphics, you may want to consider a cpu upgrade in the future to get the most out of your new GPU.
Maybe that would be okay with you. Maybe you dont care about having lower 1% lows. Maybe your gaming on a 60hz monitor and dont care about frametimes/input lag.
But for me personally, with the 2060 super and the 2600, dropping from like 200fps in most areas in apex, down to like 100fps in the big main city in the middle of the new map, wasnt good for my experience. Im competative. I was able to "feel" it. Idk if you know about "frametimes", but its basically input lag. The higher your fps, the lower your input lag. Even on a 60hz monitor, yes its still best to have a high fps even though you cant see it, because of frametimes/input lag. And ofc, the lower your fps, the higher the frametime/input lag.
I upgraded my CPU to a r7 3800x and now my 1% lows are 140fps, still basically 200fps in most areas, but there was a slight boost to the max fps and it now sits more around 215fps in most areas. So improvements on both ends.
Just something to keep in mind if you get the 2060 and wonder why your possibly not getting smooth performance across the board.
EDIT: Here is a video someone made benchmarking the 2060 super with the 2600. Pay attention to the Avg fps, and the 1% and even the 0.1% lows. Even in the 1st game of the video, you can see the pretty big difference of the Avg fps and the 1% lows. The avg is 71, and you can see the 1% low drop to 27 at some point in the 1st game. As a result, the game "skips". Take a look. This is what Im talking about when I say "smooth performance across the board"
View: https://www.youtube.com/watch?v=xhlI0qJyfsE