You wont grow 4-6 plants in a phone booth, like Joel said. He is corect.

Figure 2 sq. ft. per plant if you want full blown, full mature expression of your seed.

Your HPS is great for flower but not so great for veg.

Most of those sun master systems come with the housing and ballast built in. If that is the case with yours, the light will need to be far away to escape the heat. Your problems with light begin

I say you have the perfect setup for an SOG and plenty of light to boot.

Come young grasshoppa....follow HARD ON's FIRST SOG post and see if you want to do something like this.

You can avoid my pitfalls perhaps

You can grow maybe 2 decent plants with what you have now....but you can do so much better with an MH light for vegging.