As *Luke said, the wattage of the light determines how much light you will get, the Kelvin Temperature determines the colour of the light.
You pretty much answered what I was trying to ask?! :oops: Ha ha
I do get ok light at the bottom and plant's are growing well, nut just dont get that "brightness" I'm looking for. I'll have a play around with some different type's of bulb's I think?!