Veg is easy to do with LED. You could make something for cheaper and still get comparable results, but I'd say almost any LED grow light that you buy, so long as it covers your grow space properly, will perform well in veg.
http://www.ebay.com/itm/Cree-XM-L2-100W-Bright-White-LED-Light-Driver-Heat-sink-Heatsink-LED-LENS-Kit-/370891542342?pt=US_Light_Bulbs&var=&hash=item565adbcf46
The last option: non-dimmable 120V driver, heat sink, reflector and lens. Two of them is about the same price as the Dirt Genius panel, consumes about the same energy, and is more efficient. The Cool White light of the Crees would probably provide an easier transition for the plants over into flower under an HPS. Going from strictly Red/Blue to HPS would be quite the shock, I'd imagine. Btw, you don't need the reflector or lens, you can toss them. You just need some thermal paste to attach the LED to the heat sink, and a couple phone chargers with the right voltage/amperage to drive the heat sink fans. The only down side, imo, is ease of use with now having to hang two panels instead of one and the amount of cords (two cords per panel as opposed to one for the Dirt Genius).
Btw, I'm not quite sure that panel will cover your entire 4x2 grow space. The two Cree modules would better distribute the light over that space, imo, but I'd almost recommend adding a third unit to achieve ~37.5W per square foot. Depends how tall/fast you want the veg process to be, I guess, but 25W/ft^2 (200W / 4'x2') seems a little low, however I'm sure vegging plants would be just fine under that intensity.
