There's a company, Eastern Beaver, in Japan that makes H-4 headlight relay kits that markedly increase headlight brightness.
Their web site is <
www.easternbeaver.com> and you'll be able to get lots of information about the various models they can fit.
I have one on my maked 2003 Bandit 1200 and the lights are noticeably brighter even with the stock bulb in place. My friends have commented positively too and a couple are considering the kit, fairly priced at $49.95 including freight. Had mine in just a few days, all the way from Japan.
The relay kit has you run a heavier duty wire from the battery to the relays which then send current on to the original headlight. The kit is plug and play so to speak and is well thought out. The relays, one for high beam and one for low are easily replaced should they ever fail -- they're socket mounted and available separately.