Man, just get a nice jag and put it in the 180. Add put what you want around it. You'll make mistakes, some fish won't work out and you'll bring 'em back to your LFS. That's what everybody on MFK did when they first started, and probably still does.
You have a tank that's just big enough to house the heavy hitters, so get some and watch 'em for a few--and get ready to be impressed. You can read what we say from now on, the only way you'll truly understand what a 14 inch Jag is like to other fish in a 180 gallon tank is to watch it for yourself
You watch a Labiatus/Midevil get mature and aggressive, you'll be glad you did even if it doesn't work out.
Don't let anything get killed, but try it and see. Just have a plan if things get nasty--yours would be trade in with the LFS.
Tell us how it goes, we all love to hear fish stories.