I've done some research on this subject myself as I plan on fitting a '17 EX seat on my '14 DLX....
From what I've gathered, seats from varying years should be interchangeable as far as mounting. However, due to the varying sizes and relative shape differences at the base of the tank between the '13/'14 Standard, '14 DLX & '17 EX/RS models, there may be slight aesthetic and clearance differences at the front.
That being said, I think the differences would only be noticeable when going between a Standard model OEM seat and DLX/EX bike or vice-versa.