It's pretty easy, although time consuming to make your own headlight brightening harness using two relays. I measured voltage at the back of the alternator...13.8v and then measured the voltage at the headlight bulbs themselves. They were at 11.5v. At the headlight switch on the steering column is where I could actually feel the wires getting hot...this was with the Silverstars. The more wattage you put on the factory harness can possibly cause a fire under your dash.
After I made a "brightening harness" with two relays, the wires did not get hot anymore and the headlights had two more volts getting to them...which was substantially brighter! I guess this is the reason why when I kicked the throttle and the volt booster came on the Silverstars would blow...the were getting a lot more voltage. Since then, I've replaced the Silverstars with HID lights. They are even brighter than Silverstars and they consume less power.
HID's...