I bought a 13w HID from batteryspace (no problems with the transaction or product, fyi) and
it is more than bright enough, approximately 30% brighter than the 10W HID they sell.

The brightest, of course, is the 30W HID which is 1850 lumen, overkill IMHO. The 10W
is 550 lumen, I'm guessing the 13W is in the 650-700 range. Plenty bright. Cars see me
coming and they can't ignore me.