k, if you cant get two lamps, then you have a couple of options. 1) Get a Sun-argo HPS, it has an enhanced bleu spectrum so that it can do it all. Or 2) get a ballast that can use both HPS and MH, of called a conversion system. if you cant do that, i guess MH would work for both.
and get a clue, you might want to ask who you got the light from what kind of light it is.