I too was surprised by the poor output esp when alongside a new merc and an Audi recently after buying a z about 6 months ago (their cast was so ,much brighter, and the reach further)
I'm assuming that older xenons are not as bright ass their newer counterparts !?! but partly the reach is an illusion as your slung so low, try sitting up in the seat so your head is near roof, while parked up, you see a considerable difference- shame u cant drive with your bum off seat lol
I did however recently turn the screws by almost two full turns, so the reach is much better, and haven't had anyone flash me at night and they - were done nearly 2 months ago!