yeah 4 should do for one plant. if you can't think of a setup, go buy a lamp thats UL rated for 150W. any cheap one will do, but make sure the on/off switch is on the socket. then (if you haven't yet), buy 3 26W CFLs (2700 kelvin), and 3 26W CFLs (6500 kelvin). also, pick up 3 Y splitters for the socket of your lamp. disassemble the lamp you bought so you only have the cord and the socket. screw one Y splitter into your lamp, then one y splitter in each of the sockets of the first splitter. that'll give you four sockets to work with. and even with four 26W, you'll still be under the UL rating of the lamp. safety first!
use: 3 6500k bulbs & 1 2700 bulb for veg
use: 3 2700k bulbs & 1 6500 bulb for flower
good luck :thumbsup: