Were you planning on using these as your primary tank lights?
These systems are designed for supplemental lighting, not your primary lighting. They would be totally insufficient for reef lighting... you'd need more than you could fit over your tank to get enough.
It has nothing to do with lumens. Nor watts. I have no idea how much par one of those leds put out. but a 175 watt MH puts out about 10.000 lumens, depending on several factors.
If you're looking at a LED system that would be for your main light source, then you want to look at PFO's Solaris or Galileo, or the Aquailluminations units. Like mentioned, the Powerbrights are for suppliment.
-Justin