I myself have gotten away from SPS and just went with LPS/softies and smaller fish for a smaller tank (58 gallon) from my 135. I'd love a 135 again (minus the lighting costs) but too much for me to maintain right now.

To me it really comes down to tank dimensions due to my lack of vertical stature. I had a 180 at one time but never even set it up with it being 24" tall and 24 deep I'd feel like I'd have to go deep sea diving just to clean it. I like the size of mine now but I think if I could find the perfect 90 gallon I'd be tempted to upgrade.

Probably haven't answered any question you had but some more things to think about.