yeah you'll be fine bro.
I started out growing with CFL's only. I got good yields.. I only grow for my own personal enjoyment though. So it worked for me.. and I've seen CFL grows yield HUGE amounts.. amounts you wouldn't think would be possible with just CFL bulbs.
I then added a 150watt HPS.. the exact one you have actually.. from Sun Sytems. It's a good unit too btw..
But yeah, I re-configured my lighting setup.. and moved my CFL bulbs.. to the sides of my plant.. and hung the 150HPS up above them.
It worked really well for my needs. I was averaging anywhere from 1/2oz to 2oz yields using that setup.
About a year ago.. I went ahead and added another 150HPS to the current light configuration. Pretty much doubled my yields.. I had never been happier than I was after my first harvest with the two 150's.. and 300watts of CFL bulbs for side lighting for a total of 600 watts.
anyhow, yeah.. depending on your needs.. like how much you need to harvest.. you should be happy with the one 150.
peace.