Just because a ballast is HQI does not mean it has any additional power advantage. Most cases the double ended bulbs require a HQI ballast is because of the startup characteristics of the ballast.
http://www.fortunecity.com/meltingpo...ie/38/id33.htm
quote:
Most European MH lamps require the use of an ignitor. Standard North American MH lamps usually do not need or should not be used with ignitors. Using pulse ignition MH lamps on non-ignitor systems could cause premature lamp failure. A standard North American ballast (non-ignitor system) will cause excessive stress on the electrodes. Some pulse ignition lamps may not even light on these ballasts.