Think lumens, not watts.
A CFL typically puts out 70 lumens per watt, so your 400 W bulb has an initial output of 28000 lumens. The intensity the plants see will be determined by the reflector and the distance to the bulb, but I suspect vandas will do fine under that once you determine the right setup.
Do not bother to mix "warm" and "cool" phosphors. Find bulbs that offer a color temperature close to 6400°K, and the plants will receive the spectrum close to that of sunlight plus backscatter from a clear blue sky.
Humidity is important, but unless your basement is unusually dry, maintaining at least 50% RH shouldn't be a problem.
You will want gently, tumbling air movement 24/7, so include fans in your thinking.
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