If in flower stage, the plants need RED LIGHT WAVES and UV-B rays.

You can only get this with HPS for the red, and MH for the UV-B rays.

It is this combo in flower that helps buds grow fat and big. It is at least one of the major factors.

If HPS is not in the picture, where will the lower Kelvins come from?

Regular cheap ass light bulbs....warm....will deliver red waves. By themselves, it is a crap shoot as to the end result....

Without the intensity of HPS lighting, you need all the light you can get which means keeping the CFL AND the additions of several...the more the merrier...red wave generating light bulbs.

You can go as high as 150W regular light bulbs....you can use several....they will generate heat so air flow is critical to the success of the plan.