i'd say go for it
imo 18s don't look right on a s2, make it look like its on stilts, but saying that yours is one of the lowest i've seen on 18s and not being harsh but your wheels are out of date so a fresh look is a good idea.
16s on the deck would look cool especially deep dish, but you'll have to avoid speed bumps
put a post up in the photoshop section if you don't get any luck here