The Hawkfish may also eat your inverts....just a thought :)

I think Occelaris Clownfish are very active and entertaining! Classic--can't go wrong.

I love the Bicolor Blenny, but it may not get along with the firefish. I think they have MUCH more personality, though.

Like Zylumn said check out the nano reef link. Great general guidline for what you can keep in a smaller reef. I say six line wrasse.