Forget the K factor. Not that important. More important is the intensity of the light. If you get at least a 5500K tube, your fine.
The 'K' value for fluorescents refers to the 'color temperature'. I know this sounds funny but when you understand what 'color temperature' means, it makes sense. 'Color Temperature' refers to the temperature to which one would have to heat a "black body" source to produce light of similar spectral characteristics. So it other words the object would 'grow' at certain color at that specific heat. Kinda of interesting I think. The standard unit for color temperature is Kelvin.
About growing plants, I think that everyone would agree that the 'color temperature' or K value of the light source should match or be very close to a sunny day around noon. Am I correct?
Well, the K factor of sunlight around noon is 5500K.
About the overdriving of fluorescents, check out
http://www.myfishtank.net/cgi-bin/yabb/YaBB.pl?board=diy&action=display&num=1010380693
If you go to the reefcentral link, you will find more info, even pics for connections.
Good luck! *thumbsupsmiley*