Geoff, one of the interesting things about the VHO electronic ballasts is that they can 'overdrive' normal output flourescent bulbs. This can not be done with tar ballasts or normal output ballasts. The VHO e-ballasts have been demonstrated to actually drive NO bulbs at very near the output of the VHO bulbs. I have been using NO bulbs in my 440w VHO system for close to a year now and they work great! Talk about a major $ savings. VHO bulbs = $24.00, Home Depot 6500k 40w Phillips bulb = $4.95.
I have not found a cheap source for actinic bulbs yet, so, I still buy
URI VHO actinics but mix with the HD bulbs for the whites.
Something else to keep in mind if you are planning a lighting purchase- cost of the bulbs and frequency of replacement. My URIs look like they should last close to a year, but, the Corallifes that came with the light system didn't last 4 months and they cost about the same as the URIs. The Home Depot bulbs are almost 6 months and I will probably change them soon, but, hey! At $5 ea. twice a year, I'm still saving a bundle.

Hope this sheds a little flourescence on the subject!
