I don't own a gulper, but I've heard they have alot of personality. Maybe a breeding pair of convicts or a few firemouths? How about a couple blue acaras? 2 or 3 senegal bichirs?
IMO you should do gulpers. If you don't want them, then senegals.
I got 6 Rainbow Cichlids from AquaBid 6 wks ago that I'm thoroughly enjoying. They're in a 55 g and should be good in there for life as they only get around 3-4" tops. They're nice Cichlids, too, and you can put an Angel, some Corys, a school of some sort of Tetra or something like that in there. Mine will chase each other around once in awhile but never do any harm. They don't even look at any of their tankmates. Great fish, great color and wondeful personalites. Here's a quick shot: