I think you'd need a new ballast that would run them as high output.

Look for a workhorse ballast...with at least as much wattage as the bulb you want it to power. The high output ones say "high output" or "high power factor" on them. Premium aquatics has some workhorse 7's on clearance.

I've ordered them from prolighting before. Prolighting.com is in Michigan, but only do mail order.