I think the red sea sailfin tang is really pretty.
However...I agree that neither is really a good fit for a 90g tank. It isn't the tank inhabitants/compatibility that is the problem in my mind - it is the tank size. Both fish get up to 15" and really should be in larger tanks. They would probably be fine in your tank when they are small, but when they get to be an adult, it might not work out. The fish will probably either be stunted or get stressed out and get more aggressive (which actually might not be a problem in an aggressive tank, not sure), or sick.
I don't know who you've talked to, but if you haven't already - maybe make a post on the "reef fishes" or the "fish only & aggressive tanks" forum and see some more responses.
What about something a little smaller, like a purple tang, puffer or toby?