Yes that light would work. But more lights would be better. If your plant gets very tall and you have that one 125 watts light above it, the bottom 3/4 of the plant wont get too much light. If your plant is short and bushy that one light might do the trick
Read the growFAQ, and the part about light proximity.
You decide when the plant will flower, not the lights lol. You can flower anytime you want by switching to 12/12/ lighting. People say the buds are less dense with CFLs, but they don't have to be. With good lumens and good proximity you can grow very nice buds with cfls. Useing lots of reflective material to maximize your CFL light helps too. I'm no pro, so we'll see what the others say.
Best of luck!