lets put it this way, dont waste your money yet.
what light do you have on there now? an all glass aquarium strip light with an AGA bulb? AGA bulbs are 15w yet are 8500k on the color temp when makes them perfect for low light low tech tanks.
I got a 26g with plants as well, I use the AGA 15w stock bulb but I am getting a GE 6500K bulb for a backup, its the GE plant bulb, sell for like 6 bucks at wal-mart.
check what you got first, you might not need a bulb period.