Jhupp - I beg to differ. Yes bulbs can vary considerbly, most people have only the color temperature and other published stats. It does mean something even if indirectly. Higher lumens will mean more usable light which means higher rates of photosynthesis. Color temperature indicates the color balance which will give a good basis for knowing the ratio of blue/red since most of us don't have the ability to generate spectral charts of measure PAR directly.
The bulb your using is GE's 6500k daylight bulb. A very nice bulb indeed with excellent lumen output compared to many other 40w bulbs and shifted towards the blue so that more of the light will be usable by chlorophyll A. Especially since these bulbs are only a few bucks more than a standard cool white shoplight, they are well worth checking out.