Maybe I'm just not reading this right, but onah said he wanted the highest he could go WITHOUT having CO2. which means we are looking at around 2 WPG.
So the only viable solution would be one shoplight with 2 T-8's or the equivalent.
docrak, JDogg was giving WPG based on lumens not actual wattage. T-8's are more efficient then T-12's and therefore give off more light per watt. Remember the WPG rule was based on T-12's.
reference:
http://woo.gotdns.com/Aquarium/Lighting.htm
calc's: 2 (bulbs) x 32 (watts) x 1.49 (T8 outputs 149% of the light that a T12 does) / 55 (tank size) = 1.73 WPG (JDogg's WPG)
Ok now lets look at the light you posted docrak,
first off it has two Actinic bulbs which are just a waste of money for growing plants. but anyways,
4 (bulbs) x 64 (watts) x 1.35 (Compact Fluorescents are more efficient then T-12's, but not as efficient as T-8's) / 55 (tank size) = 6.28 WPG of course this would be if you replaced the acinic bulbs.