Light intensity is the important factor, not the total amount of light. A 100W domestic lightbulb is quite "bright" in a closet but pretty insignificant in a football stadium. So a 400W metal halide will burn any plant, low light or full sun lover, if you place it too close. The same 400W metal halide will not keep even the deepest shade lover alive if you place it too far away and spread out the light too much.

so for low light plants, how far away from a 400W should I keep them, what about a 1000W. Right now I have everything under separate 4 four foot flouro fixtures approx 20 inches above the plants, and I have been thinking about moving them to the basement where I have MH HID lights, mainly hoyas and gessies, as AV's are kept under other lights.