Do they need to be really aggressive? I'm setting up my 120 with Uaru, Severums, Chocolate Cichlids, Firemouths and maybe Festivums, along with Tiger Barbs and Clown Loaches.
I especially love the Uaru. They are so graceful. Here is a pic of a Chocolate, Uaru and a young Gold Severum in my 60 gallon tank -
The Chocolates and Uaru will eventually get a little over 8" (not much over). The Firemouths (great breeders), Severums, and Festivums will not.
Others you may want to look at are Brasiliensis, Blue Acara, Nicaraguense, Centrarchus (great breeders), Jurupari.... hmmm there are many others.... I'll need to think about it.