Just as a follow up to this ... I ended up getting a shimano alfine hub front wheel ( got it complete from rosebikes.de )

And then bought an supernova e3 triple as the front light ( from Bike24 )



Only had the chance to ride it once in the night, but I have to say, its really very very good.
I had been riding a homebrew light setup of twin P4's. I'd say the e3 triple matches them in terms of light output once youre upto speed. Most of my commute is along tarmac'ed cycle paths with some on the road. the beam lights up the path and verges nicely and is more that enough to see by even if the surface is wet.
I cant say I notice the drag of the hub. I tried with the light on and off, and couldn't notice a difference.
for commuting, its so good not to have to worry about recharging the lights. It now means I can adapt my homebrew ones to another, more powerful setup for other bikes where I know my rides are going to be shorter.