I would try to match what you already have. I noted your other thread where you said you had one and were looking for another. Ballast to ballast combined with different bulbs can cause different colors and intensities which may drive you nuts
I have to say that up until a few days ago, I liked the pheonix 14k se 250 drivin on PFO hqi ballasts... But I just picked up a 400 watt PFO HQI ballast with a helios 20K and I have to say that I have a new favorite combo It is very crisp white, with just enough blue tinge that the corals absolutely pop. And with a PPFD of 149, it should grow just about anything in a 30" deep tank.
But anyway enough of my rambling... The point was I would match what you already have and then look for a color you like with enough par to grow what you want and which depth Just another IMO though...
They are fine. hellolights seems to have good prices. Where you will get more expensive is w/the ballast. That link is for a magenitic ballast. Electronic ballast are more efficient and don't run the bulb to the peak power where metal ballast do. Electronic ballast also are cooler and you get a little more life out of your bulbs.