My goal as well is to get a 125 gallon tank when I am finally able to buy a house. (I think I'm going to meet with my bank this week to explore the possibility...
)
Anyway, I always thought a 125 was perfect. It's huge, big enough for pretty much any fish you want to get. And with 6 feet of tank you can make a REALLY beautiful reefscape. That also gives the fish plenty of swimming room. Additionally it's not so deep that you need lights built by NASA to keep your corals alive.