In that case, the light makes the difference.
If you decide to go for the HPS1000, I STRONGLY recommend a good exhaust fan connected to an air-cooled hood. Aim for a 200+ cfm fan!
It's good that you vegged extra time if you are only growing 4 plants under a big light in that space. I'd personally grow 36 small plants SOG on a 4x4 runoff tray in that space. You can set it up in many configurations, depending on what STYLE of hydro you prefer. But longer veg=fewer, larger plants to fill the same space. Try to train them as flat as possible as you are flowering them, and then let the buds grow up straight with no more training after the 'stretch' period is over (2-3 weeks in).