My approach to the three centrefires is: 22.250Rem, 270Win, 300WinMag. My rationale is that they are ballistically very similar, with a very good range of bullet weight across the piece - 35-65gr from 22.250, 90-160 in 270, 110-220 in 300WM.
I can shoot pretty much anything, anywhere.
Given your 6.5-284 is already in hand, I'd keep that unless you desperately want a change. TBH, the 22C/F all cover pretty well - and if you're going above your 6.5, you may as well pick a rifle with significantly more energy to lay down - so one of the 300 Magnums (RUM perhaps?) seems a good choice.