Dude if I had a tank this big I would so go reef. I had several fresh tanks two years ago for several years, but when I bought my 125(I know so miniscule compared to yours) I decided I wanted a reef tank. I used to be on here talking about how saltwater sucked and it cost to much. Well yes it does cost, but it is so much more rewarding IMO.
The colors and behaviors of the fish are much much different than fw set-ups. In all my tanks my cichlids just wanted to kill each other. Now my fish live in harmony and its such a diverse community that you are able to keep together that actually get along.
A huge tang colony would be sweet as would some large angels. Emperor's and Scribbled angels are some of my favorites as are the goldflake's, conspics, and blue faced angels. Also a big FOWLR aggressive tank would be awesome too. Some large triggers like a Clown, Niger, Blue Face, Crosshatch would be cool along with a couple eels like a snowflake, zebra, and or a tesslata, although the tessy would probably mess with the snowflake or zebra unless they were full grown. You have some thinking to do although if you went reef with corals you'd need at least 1000w halides seeing as how your tank is 5' tall. It would cost a lot, and you'd need to seriously re-do your filtration. Like adding a big sump, big skimmer and some reactors for carbon and GFO and some Bio Pellets. You could skip the bio pellets if you got a fluidized bed reactor for nitrates since having big fish means big nitrates and phosphates. If you went FOWLR though you could get away with 250w MH's instead, but I'd probably use 400w. BTW I saw your thread on RC and thought I would check it out since I am a member here and all and haven't been on here in a long time. I see it hasn't changed much
Good luck!