You have a great benchmark ball. From there I would add a 920T due to it's versatility and closeout price. From there you have some hard decisions to make. If you want a true heavy oiler you can go with the 715T, but if you want a ball for the heavy that you can do more with surface prep you should go with the 916AT. Now below that you can go with a few different options. Personally, I would go with a 715A as it will give you a different look than the 715C, and then I'd wait for the eventual 505C replacement as your go to med/dry lane ball.