Well, I really have no idea what retrofit really means, so I guess I am in the process of getting the whole darn setup. Like I said I would like it to have 2 x 250 watt MH, 2 VHO's (1 actinic 1 white bulb), and two cooling fans. One more thing I was wodering... how strong should I get the VHO's... I have no idea what 10,000k stands for on my PC's now, and what wattage for both bulbs?