I use a set of Eastern Beaver headlight relays, with a home made harness. I figure the whole deal cost me about $30.00 or thereabouts. Took maybe an hour to solder up the harness. Previously, when things were stock, the voltage to run the headlight had to wind its way through the wiring harness, then go through the handlebar hi/lo switch to get to the bulb. There was at least a 1.5 volt drop by the time it got to the bulb.. I never liked having the high amps running through those little connectors in the switch, which kept me from getting one of those monster bright H4 bulbs. However, with relays, you are running the bulb directly from the battery, through (in my case) 10 gauge wiring, right through a ceramic connector to bulb. All the hi/lo switch on the handlebar does now is trigger the relays. Put a fuse holder inline from the battery to the light, and use heavy wiring and a ceramic bulb socket, and you could easily run a high watt bulb. This information is based on the supposition that your charging system is up to snuff, and you have a good battery. I'm running a RMStator high-output Venture Royale stator, hard wired to a Shindengen SH775 Series regulator, all directly wired with 10 gauge wires directly to battery. Even with a stock H4 bulb, the headlight on this bike is amazingly blindingly bright.
If you do one of these LED conversions, or one of the HID setups, and you have a problem, you're stuck till the sun comes up. H4 bulbs are available everywhere, and I'll put the light output of my bike up against any of the LED or HID setups.