I reckon you could drop the King and just use 1 Vipar over each plant. Might have to have them a little lower but 185w/hour less use is 185w/hour less on your electric bill AND you have the option of dropping in a third plant with the King over it if you wish.
You're looking at each Vipar being the equivalent of a 200w HID, and by only using them you'll save around 100kwh, the unit they use to calculate your electricity bill, per month on an 18/6 schedule. No idea how much your electricity is per "unit", but the savings over a year are not to be sniffed at AND you'll have a spare light should one of the Vipars go Pffzzzt.