Just change to better halogen bulbs like Phillips Xtreme Vision or Osram Night Breaker Plus, should be more than enough. Unless you want bright white light HID look which is difficult achieve with normal bulbs as they need to be slightly yellow like std bulb in order to give maximum brightness. You can also opt to change to whiter 4000-4500k bulbs (Phillips Crystal Vision, Osram Cool Blue Intense, PIAA Northern Light) but it would not be able to shine the roads as clear as Xtreme Vision or the like, but it may still be a bit brighter than std bulbs. The whiter ones would look nicer though.

I'm using PIAA Northern Light which is 4400k and still legal. Crystal Vision is 4300k while Cool Blue Intense is only 4200k so they're also still legal.