thats a good size, it will leave plenty of room for all your equipment, and plenty of macro to keep those phosphates in check. i wanted to use a 55 gal on my 90 but it wont fit underneath my stand. sice vie been looking for a 40 gal.
i've heard a variety of "rules" ranging from 10%-35% of your total tank volume. Anything in that range would be covered, in your case, so i say go for it!
In the world of saltwater bigger is generally better. Greater volume equals greater room for mistake. It's a lot easier to manage the increase of bioload when adding livestock to a tank in a huge system than in a small one, such as those in nano and pico reefs.
+1 for the comment on added space.
a 55gal fuge should allow plenty of space for chaeto, LR rubble, reactors and skimmers, as well as your heaters! Should really help clean up the appearance of your display.