I'm kind of curious myself as I plan to buy a 125 gallon (72x18x22) within the next 3 months. From my research, I was planning to put in 100 lbs. of live sand and 90 lbs. of live rock and hope that my sand bed was deep enough. I am currently trying to decide on an appropriate protein skimmer and powerhead.
I wasn't planning on having a sump at this point, as I'm not quite sure I understand what the benefit is and how to integrate it with the system I will be having.
I haven't decided on livestock either, but I think I want to stock it with dwarf angelfish of different colors, critters for a cleanup crew, a cleaner shrimp, and some really exotic ugly looking fish once I find an appropriate one. But I doubt I'll get fish into the thing until next spring.