Sounds like you actually have a 75 gallon rather than a 55. Four 55w
CFs would give you a nice amount of light, but very close to too much
for a non-pressurized CO2 setup. I would aim slightly lower if you
plan to use DIY CO2. But still, if you have the patience to keep up
with them, a couple DIY CO2 bottles will work for you. I wouldn't
waste any money on off-the-shelf DIY CO2, they are no better than
regular DIY yeast/sugar mixes, save the money for a pressurized setup.
As for the lighting, again probably a little too long, I'd start with
10-12 hours and see how things go, you may find yourself reducing it
if you run into any problems. Filter wise, the 2217 is what I use on
both 55 and 90 gallon tanks so I know that will work very well for
you. The 2028 is just as good, pretty much the same size, a little
bigger media storage I believe but very much the same. The HOB you can
throw out the window, it's only going to reduce your CO2 levels and
it's not needed as any one of the other filters you have is more than
sufficient. A good size fish load may also help maintain higher CO2
levels, but obviously don't go overboard. As for the substrate,
flourite/gravel mix works well, I'd add a handfull of peat moss to the
lowest layer along with 5-6 crushed Flourish Tabs. Then cap it all
with 3-4 inches of flourite/gravel mix. I don't think you'll be able
to maintain such a steep slope for too long (4" in back, 1/2-3/4" in
front) plus that could cause nutrients to come out of the lower layers
of the substrate. I'd go with 4" in the back and 3" in front, all the
same gravel/flourite mix in case you decide you want some foreground
plants in the future.

Here's some basic info regarding DIY CO2 setups:
http://www.gpodio.com/diy_co2.asp

Hope that helps
Giancarlo Podio