Rather than replacing older equipment in a single large purchase, consider introducing one new platform, a smaller-scale solution in parallel with the existing systems. We’re splitting the difference here.
It may be less expensive to add a new platform than to grow an existing one. It can take a little pressure off an older storage array and give it just the breathing room it needs in terms of capacity and performance, to stretch it one more year.
From file and email servers to databases, archives, and backup, storage takes on many different shapes. Because of this, performance and manageability should be higher considerations than capacity.