Since you're using CFLs I'd say the more the merrier.

Get some Y adapters and throw at least two more, if not four more bulbs in there.

HD has some 40w 2700k 550 lummen CFLs in a four pack for about 6 bucks, personally I'd look into that...

EDIT: And, hang the bulbs low so that plenty of light penetrates into the sides of the plants.