Well lets see, if you are looking for something other than cichlids have u ever thought about the hoplias family. You have the red hi-fin wolves, Gold wolves, and Common Wolves. All three are less active for the most part than most cichlids except at night since they tend to be more active nocturnally. But these guys are Super Aggressive and they get meaner as they go up in size. The Red Hi-Fins get between 8-10in, Gold wolves get around 16-18in, and the Commons get anywhere from 20-24in. The Commons are the least active out the three, but the meanest and jus cuz they dont move alot doesnt mean they are slow. They are incredibly fast and accurate and have the jaws of pitbulls...Ive seen em in action. Since you are in the US Snakeheads of course are illegal if im not mistaken. Gobies arent really aggressive unless you are something half they're size, they eat like PIGS...LOL...Or if you are wanting to try something really different maybe Fahaka puffers....great fish lots of personality and are super aggressive. Hope this helps...