i did just that 10 months ago
after more then 15 years of reefing with a standard 125 i started over
key points:
1) tank - 36x36x24 shape is everything
2) flow - gyre type flow pattern with placement of pumps designed into the reefscape
3) lighting - T5, more choices and better color
4) sump - in basement, summer cooler, larger sumps plumbed together, more volume
5) scape - open yet has a large surface area done with caves, overhangs, and 6 - 12" all the way around front, back, and sides for flow
6) corals - choice pieces well placed with growth, shape, color, and aggresion all considered
7) ease - 2 part, kalk, bacteria and a good skimmer - kiss
8) nature over technology - cheato, cryptic, detritus settling areas all included in sump
9) display bb so no sand to maintain
10) fish - functional as well as nice looking combos
hmm what else ??? i know there is more but that would be where i started