Light bulbs-- what brand/K

Im looking into buying my first light(s). Ideally I will use the light in a 4x4x8 closet. I will divide the closet into an upper and lower sections, both having apprx. 4ft vertical space. I already own two 175W mh/hps ballasts. I was thinking of using one for vegg, and one for flowering. Obviously i could use a MH bulb for vegg and HPS for flowering. How many plants (in my space) will a 175W bulb adequately grow? I will be using mylar on the walls. Also is their a preferred brand or K rating for the MH and HPS bulbs?
I do have the option of buying new ballast/bulbs if necessary, but i would love to use what i have..
Thanx!