I used 2x 400w HPS and CFL sides before I switched. A general rule of thumb when shopping - look to replace HID with anywhere from 1/2 to 2/3 the wattage you had with HID (output wattage on a true 3w chipset lamp). If you read the journal you probably saw I'm of the opinion you'd be better served having several smaller wattage units to give you a modular set up. If you have 3 units pushing 130-150w of actual output not chipset capacity (which most companies advertise), that should equal if not be more than a 600w hps.
I'm spitballing as I never had a 600, just the two 400, but I was running 1200-1300 of wattage at any given time and now use about 600w of led output - no drop in yield and my buds aren't burnt.
been growing for years in and out .a good led light is bad ass.Ebay will not have what you are looking for.Do your research befor buying more money does not mean a better light
indeed, although you can sometimes find stellar deals on ebay. I got one of my spectras and one of my pro grows from hydro hut at a serious discount. Like beardietree said, just do your homework before you run out and buy something.