depends on the lighting. 100w cfl will not perform the same as 100w of led(china panel), cob, hps, or mh. the question you ask simply cant be answered without more information. in a 19"X19" space you wont need much more than a 60w cob or 2. i run 3 in a 2X4 tent and my lights had to be raised to 18" because they were burning my tallest plant. i may even look into buying drivers with dimmers.
personally, i run a single 60w cob for each plant, but im new to this and may change that in the future. in your case it would be great because you can buy multiple cobs allowing you to diversify spectrum for about $75 per light.
but hey, im a cob whore.