What do you think are the best lights for sour diesel?

This article was originally published on the Marijuana Patients Organization site on September 30, 2011.

Sour Diesel works well for my treatment and have a great strain that I grew once before and turned out well in soil. Had 600w HPS for 6 plants but little yield. Need to harvest 12 ounces over harvest for me and my patients. How to best do this? What type lights and how many?

Want to stay with dirt and feel comfortable their and ventilation, etc feel are adequate. Thank you for your help

Vincent L.