best spectrum for AUTOFLOWERINGS

i was just wondering what you guys think the best spectrum for growing auto flwoerings is? is HPS really neseccary for autos? or cfl should be enough?

cheers guys

CFL's will do you just fine in a small space for two autos, and they use the same light spectrum as photo plants, blue for veging and red for flowering.
Just keep the cfl's about 2 inches from the tops and you should be fine, and maybe look into indica dominant autos.