I say take your 20 gauge and go shoot , you may find you love it or may find you don't care for it . Why buy an expensive gun and possibly find out you don't like the sport , you are no good or that it just doesn't do anything for you ? When at the range I'm sure other guys would be willing to let you try their shotguns , another good way to weed out what you like vs. don't like .
I know this article is 5 years old but I found it to be a good read when I was looking for an O/U . I ended up with a Stevens 12 gauge from a local gun retailer . I don't spend big money on guns but big money is a different amount for everyone . For me 700.00 - 800.00 is the limit . Good luck and hope you enjoy the sport .
https://www.outdoorlife.com/photos/gallery/guns/shotguns/double-guns/2012/11/best-over-under-shotguns-less-1000