There are a few different bulbs type:
1) Single beam system (No highbeam function - it's so bright, you might not need it)
2) Dual beam system (Xenon for low beam and halogen for high)
3) Bi-Xenon system (Xenon for highs and lows. For highbeam, the bulb is mechanicaly tilted by an actuator)
4) True Bi-Xenon (Xenon for highs and lows. This system will come with 4 ballasts) - most expensive.
For brighter whiter lights, I would go with the 6000K color. The higher the color temperature the more blue the light will be and also the lower the lumens output of the light will be. Just to put things in persective, the average lumens for halogen lights is about 1200 and for xenon is about 3000 for 6000K bulbs and slightly lower for higher color temperature bulbs. You can definitely tell that the lights are much brighter than halogens and they don't run any hotter than halogens. They draw less power than halogens 35w vs 65w so less heat is generated. It's kind of like fluorescent light theory (cool brighter lights with less power draw)
None of these retro-fit systems are DOT approved. I'm not concerned with that. I just want to be able to see better on back roads. When I go to the inspection station every 2 years, I'll just temporary put my stock halogen bulbs back on and bypass the ballasts. They'll never know the difference.
