I would always have problems with brown algae in my tanks back when I had very low light and my common plec would always completely take care of the brown algae in about 2 weeks. I'm not an expert, that's just my personal opinion.
One more thing, I really really don't recommend that you upgrade your lighting unless you have live plants (Fish don't really need a lot of light) It will be 10x harder to get rid of all the other type of algae that will come up in a tank with more light if not properly taken care of from the beginning.
if you really want to go the chemical route
I'd recomend eSHa protalon-707
it really is the best, IMHO, for killing algea
(not sure it is available in the states though)