Hi,
I'm in the process of setting up a Nano Reef Aquarium around the same volume as your own. Upon research I am just going with the 2 Ocellaris clowns.
Regards
BigC
Personally, I"m not a damsel fan. If you get 2 ocellaris clowns, make sure they are either very small or paired or they can fight. Why not go with a single clown and a purple firefish which is a gorgeous fish? SH