If you want them brighter you don't want blue. The more blue you go, the darker the coating on the bulb, which means less light output. I see some cars with really blue lights and I can't figure out how they can see where the hell they are going. True HID is different, since it is the gas mixture that creates the color rather than a coating on the bulb. Even so, a 4300K HID puts out more lumens than a 7000K HID.

As far as Silverstars are concerned, they just aren't what they claim. The light appears brighter because it's whiter, but you actually lose overall light output. You end up with a brighter area directly in front of you at the expense of distance. Plus the Silverstars we get here aren't even real Silverstars, just regular cheap halogen bulbs with purple coating on them. The real Silverstars are clear glass and have a tighter filament winding, which makes them brighter, but not more blue. The closest you can find to a real Silverstar is probably the Phillips Vision Plus, I think it is.

BTW, I had a Silverstar drop dead within just a couple weeks. In comparison, my PIAA Extreme Whites (which I like, but won't spend money on again), have lasted nearly 4 years.