lighting for a 10g nano

[outtafocus]

I dont really believe in this watts per gallon method of lighting.
If you had a 1gal tank with a 10w bulb over it, thats also 10w/gal but probably not enough to grow much.
I am running a 150w HQI MH over my 25gal cube. When I bought the light I every one on Nano-reef told me I didnt have enough light. But 150w over a 25 is 6w/gal, which I have read on many information sites online is in the upper end of the watts/gal ratio. I am very happy with the 150w over my 25, any more would be too much.
I am only new to this game so I may be way off base. But it seems everyone one with beautiful nano tanks are using alot more light than what would normally be needed.
Opinions?