I've fitted a set of Givi Trekker lamps to my F650GS.
The original 55W bulbs ran the battery down making it hard work to start the bike the next day, so I fitted LEDs. The funny thing about the bulb fitting in these lamps is that they are fitted at 90 degrees to the reflector and not the normal inline way. I found the LEDs had a blind spot as you looked at the lamp directly and the beam pattern was had a large dark portion in the centre when projected onto a wall.
My solution has been to fit 35W H3 bulbs. I hope the lower Wattage will give the battery more of a chance.
I fail to understand why folk say these bulbs are expensive? They are standard H3 halogen bulbs with a flying lead and can be bought at almost every motor factors.
These are the bulbs I bought.
http://www.ebay.co.uk/itm/141331925295? ... EBIDX%3AIT