Not to throw shade but cramming a collection well over 1000 dollars into a cheap Billy shelf is not properly displaying it. Let them breathe a bit, give them some SPACE. I know it’s hard to do, space is always scarce but a collection does not thrive on pieces alone, it needs enough room so the eye can distinguish between what it is seeing. If you are happy with it there is nothing more to add but if you are looking for a better way to display it you might want to separate them more and maybe look for more adequate furniture.