Matt, your tank's looking great!
The clamp lamp/CFL route is particularly interesting because it's so CHEAP to swap bulbs and adjust color temps and wattages. Matt and I went the Lowes/Home Depot route, but eventually I ended up using Zoo Med "Deep Dome Lamp" fixtures because I wanted to hang them pendulum style and the standard clamp lamp shades are shallow, allowing the bottom of the bulb to protrude below the rim and blasting light into the room. I also liked them because they're black and my tank trim/stand is black.
Here are a few pix of my tank right after I changed to it from a 30 gallon, so the plants are a bit...um...wild ;-)
This is a 40 gallon breeder, which is 17" high
If you go high light you will definitely want pressurized CO2. You will struggle with algae without it on a 55 gallon tank. I got a used regulator, drop checker, needle valve, solenoid,. and 10 lb CO2 tank that was 80% full off a guy on Craigslist for next to nothing ($50 for all that AND another regulator with a blown low pressure gauge). I bought an additional backup cylinder for $25 from a used restaurant equipment joint. You don't need aluminum - that's all bling and additional money for essentially nothing. Airgas Inc, and Haun Welding Supply will SWAP any cylinder one-for-one, and for your $18 you get a freshly painted bottle all cleaned up with 10lbs of gas. My 80% full 10 pounder has been on my aquarium for 4 months now at 3 bubbles per sec and has about 600 lbs of pressure left. At 500 lbs I'll switch out that tank for the backup.. So...6-8 months out of 10 lbs @ 3 BPS...
Be careful with your light - it will drive your need for every other parameter. Ferts, CO2, general maintenance all revolve around how much light you jam into the tank.
Good luck - there's some good advice floating around here!