dont know how reef safe the little pnks are, but i have always wanted to do 7 or so domino damsels as they will school together and are an interesting fish that wont break the bank buying so many. saw some on DFS actually sold as a group of 5 with a rose nem as they apparently host it and i think a tank dedicated to that would be awesome looking.
another cool fish is the silver cardinal, sorry, cant remember their exact name. sirricsalot has something like 20 or 30 and they look so cool schooling together. im sure you could get 5 and still get a nice schooling affect.
i too have had a threesome of chromis which have been fun, but in my 210 i plan on doing 5 of the smaller anthias. again, i know you havnt had much luck with them, but there are other types that are not so difficult you could read up and find. great colorful fish.