another light

I've got a 5 x 10 x 8 room that I run 2 OG 8" reflectors in. I'd like to add one more light in the middle. What would be best? Im thinking a 600 mh or the like in a cool tube...

I should add that this is my flower room only, and those are 2k of hps. Its gets kinda dark in between the two but I don't think I really need another 1k.