Another fish you could try is a hawkfish.. Several different variations, the flame hawk is especially nice.. I've kept them on and off throughout the years, and they are amusing to watch..
As for the chromis question, I used to always use blue/green chromis to cycle my tanks, back before live rock became popular to cycle, and no matter how much you start out with (I've started out with 3,5,8) they always end up killing each other.. Not sure on the blue reef, I've never kept one..
Striped damsels along with most damsels get very aggressive.. They'll chase other fish, nip at them, stuff like that..
Cardinals do better in schools, I have 3 currently in my tank.. Swim together when I have the moonlight on..
If u do keep clowns, they can get aggressive, it really depends on the fish, more so when they get older as well..
I'd start off with the cardinalfish, maybe a royal gramma or firefish..