Watts up?

I've seen the rule about 2w per gallon of water, question is, what's with
the specialty lighting, such as powerglow and aquaglow, is that a way to
artificially increase energy output for the plants without increasing the
wattage?

Just curious as I have a 40w in my 90g, it's an Aquaglow. it's an oddball
size, 42". It's the highest wattage light I can get in a 42". I can switch
to paired 24" flourescents, but I'd need to cover the entire top of the tank
with them to get anywhere close to the wattage required.

What ideas can you guys give that actually increase the wattage that high or
do the specialty lights actually do the trick? Is there an aquarium branded
light that goes that high wattage, or do you switch to shop lights and make
your own set-ups?