I'm going to make a lot of enemies by saying this, but Silverstars are NOT brighter. They use the same wattage as standard headlamps, 51W low beam, 60W high beam. They have a blue tint on them to make the color temp look hotter, and of course this blue tint absorbs some usable light. Do not fall for their marketing claims that they are "whiter" and "brighter," it's all 100% false. (Of course "whiter" is subjective, and as such, an easy scam to market without getting into legal trouble.)
When I worked in the automotive industry my company had some of the then-new "hyper white" lamps tested, and the PIAAs were the best performers because they only lost 15% light ouput compared to stock uncoated lamps. The worst performers lost over 55% performance compared to uncoated. Back then, my favorite phrase was "Where can we get more of these placebos?"
A couple others have suggested overwattage lamps, and these are about the only thing (except HIRs) that can output more light from the stock housing without going through a huge conversion. Of course, there are various safety issues that would have to be addressed (wiring capabilities, extra heat in the housing, etc).
This company is not related to the forum, but they have a very knowledgeable sales staff:
http://www.candlepowerinc.com/
They're in Canada but friendly to U.S. sales.