Does LUX Matter?

Hi all...
In my futile attempts to grow plants in my fish tank, I just purchased
a Hagen Sun Glo which has 125 Lux reading for a 24" bulb, which I
assume could grow some plants. On my next trip back to the Fish Store
I notice a Hagen Life Glo which had 235 Lux reading. Apparently, as I
understand it, Lux is a reading of Light Intensity (in a nutshell). So
I'm wondering if a light with a higher Lux reading is better at
growing plants, than say one with a lower reading. I am currently
searching for the most powerful florescent tube I can find to grow
plants in my 29gal. I realize spectrum has a lot to do with how well
plants grow, but with only 2 tubes over my 29gal I need all the
intensity I can get, right?

Thoughts, Suggestions?

Thanks,
Nick D.