I too use the SunSystems 150w HPS. I've got the conversion bulb for it too. Started out with just one.. but then I bought another one. Paid well under 2 bills for both units. They're a bad ass little unit for being just 150watts. Brighter than you think they are..
I've had both my units ever since I started growing almost 4 years ago. Quality ballast in them.. the only thing I've had an issue with.. was one of them started buzzing like a street light does sometimes you know? It was the ballast.. I knew what that sound was right when I heard it. It only did it for a few days during the hotter months of the summer time.. but its never done it since that one time.
But yeah, they're def. a good quality unit for the price.. and brighter than you would imagine them being.
peace..