I currently have a standard 55g tank with two 24" single bulb light fixtures on it. They are the standard fluorescent bulbs that came with the tank. I have a few plants:

Amazon swords
Anubias (I think)
Melon sword?
Anacharis
some sort of grass - Cyperus Helferi?
Vallisneria spiralis
java moss
Christmas moss (not in tank yet. Ordered)

The plants aren't exactly thriving, but they aren't dying either. I really don't want to get too high tech with co2 and stuff like that if I don't have to. Is there a decent bulb upgrade I can get that would do the trick, or am I trying to oversimplify it?