balistik1- Do your 20K bulbs now have a bluish tint to them like most 20K's have? If so I would suggest splitting up the additional VHO bulbs to 2 Atintic and 2 10,000K. That way you have more "white" light for a better look as well as the 10,000K is better for growth (I think) :notsure: Please correct me if I'm wrong.
Squidd is right as far as the magnetic ballast. It would drive the 150W bulbs more providing more par.
If you went with the 3 150W DE HQI 20,000K and 2 72" VHO Actintic and 2 72" VHO 10,000K that would give you a total of about 9W per gallon. EXCELLENT for pretty much any type of coral.
IMO that is the way you should go.