I had a 1660 super that I sold a while back(double what I paid for it), then had a gtx 970 as a stopgap card, but ended up getting antsy and bought a 1070 so sold the 970 and am keeping the 1070. Pretty much broke even I suppose.
Now that you know my story there lol, the 1660 super is roughly equivalent to a 1070.
Have you considered letting the 480 stay on and upgrade cpu board and ram? Those are more affordable at the moment. To be honest, you’re older i7 is a little worse off than a new i3 as those are now quads with hyper threading, and should be higher single core performance. You might consider that route.
On the flip side if you sell the 480, some of the 480s and 580s were selling for 400-800 for 8gb cards. So maybe you could go 2060 or 2060 Super or maybe 3060 even and sell the 480?
Edit. I guess it looks like now 8gb rx 480s on eBay are going 300-350. Count on eBay I think to take like 20%. So maybe 30-40 of the sale?