have you considered humidity trays?
also, grouping plants together will help create a microclimate around them. you can also use that as an excuse when your wife wants an explanation after you bring home more orchids...
use as many bulbs as you need to light all the plants with the bulb approx. 12'' above them.
if your bulbs get very hot it might be necessary to hang them higher, leaves should feel cool to touch.
your oncidiums will appreciate more light than others.