Clamp lamps will work just fine on a 55. I think 4 would be ideal, since a 55 is 48" long and you can get 10" clamp lamps. I would *strongly* suggest you start with 13w CFLs rather than 23w because your aquarium will be new and you will struggle with the various algaes that pop up. 13w will be more than ample for your needs. I can't emphasize this enough. The #1 mistake people make is over-driving with light.
That's great advice. Thank you! My only question though, with 13w bulbs vs 23w will the 13 matters be enough light to sustain plants above the low light plant range? I am interested in doing all of the medium to high light plants with this tank. I don't really want to buy one set of bulbs only to replace them again. I know they aren't expensive but I hate wasting money.