When considering lighting, you should think about how much work you want to put into the tank. The more light, the more attention it will need.
In your case 110w/PC(power compact) would give you, what I consider to be, a low/medium light situation.
You would be able to grow many types of plants, but would have a difficult time growing most plants that are red, and some ground cover/grass type plants(small, foreground plants).
55s are 18" deep which makes light penetration an issue.
AH's 2X55 watt PC would be an excellent choice for you to start off with.
Here's a link:
http://www.ahsupply.com/
Click on the 55 watt kits and you'll get an idea of what's available, and costs.
Assuming that you have the typical dual hood set up that comes with many 55s, you would 'retro-fit' them with the kit that comes from AH.
Len