Lighting question

I'm sure this has probably been asked to death in here, but I recently
set up a 20 gallon tall tank I acquired and have put various plants in
it with a laterite substrate. They are all low to moderate light plants
(Java ferns, dwarf sag., anubias, and various crypts). Now the problem
arises with the lighting. It only has a 15W fluorescent hood that came
with tank. I've since replaced the bulb for one with a more favorable
spectrum. I'm pretty sure this still isn't enough light, though. So,
if I make a trip to Home Depot and pick up a shop light and put full
spectrum bulbs in it and hang it over the tank with a glass hood on it,
will I experience better results? I don't have much to spend, and this
seems to be the most economical way to solve this problem. Any help
would be appreciated.

Sorry for any horrid grammaratical errors, it's late and I don't think
I'm even awake anymore.

Thanks,
--
dan