This may not exactly answer your question, but I hope it helps. I was having
trouble growi`````n`g sun loving plants in a southern window. They just did
not get enough light. I got a plant stand, it kind of spirals up, then put a
stand lamp with three adjustable lights that I could point anywhere I want
beside the plants. I also bought the highest light output compact
flouescents I could find. The plants thrive under this light. I have
geraniums, begonia, cyclamen, a miniature rose that's waiting for it to warm
up enough to plant outside, and others. I don't think a regular flourescent
lamp will give enough light. The only problem I've had is the CFs have
burneed out after only about 6 months. I may have to drill some holes in the
lamp covers to let some heat escape.

Do you have a list of herbs you want to grow? I wouldn't grow mint
(reproduces rapidly) or sage (gets too big). You could try rosemary, thyme,
and chives.