After seeing many many posts especially lately in these forums about people wanting either projectors or HIDS, I have decided to put this post together covering aspects of both.
To start with, 95-99 cavaliers have two seperate bulbs 9006/9005 for low and high beams respectively(Correct me if I am wrong) The 00+ cavaliers have 9007 bulbs which function as both the high and low beams.
Bulb Color
The colors of available bulbs vary greatly. Many people wish to lose the stock yellowish lights for different bulbs. Many bulbs have temperature ratings which associate them with a color, 4300k is a white light, 6000k is a blue/white, 8000k is a bright blue, 12000k is purple. That being said the higher the number, the less visible light that is put out so a purple bulb puts out the least amount of light out of everything.
As far as bulbs go if you are looking for a nice bright white lite, Sylvania Silverstars are great bulbs, they have a very very light blue tint to none at all, but have great light output.
For those who want a blue light, I personally suggest StreetGlow EuroLites Series, They give a very bright light, with a blue hue to them. A good mix of color and output.
The same temperature rating works for a HID bulb system.
HIDS
Many people want the HID output and look, but do not fully understand the workings of a headlight housing. The chrome reflector housing is designed for the specific bulb size which your car uses. The pattern of the reflector is designed to aim the light produced by the bulb in a certain way, since normally people just replace bulbs when they burn out, it is the same size and the pattern of reflection is the same.
When people attempt to put in HID kits, the bulb size is much different although it has a base made to fit your cars stock holes. The bulb is much smaller in diameter, and longer. This changes the way light is produced and reflected, which causes the beam pattern to be different, in turn possibly throwing light in directions it was not intended to.(across the lane into oncomming traffics eyes)
A HID kit consists of a HID bulb, and a ballast basically. The ballast is a control box which changes from your cars plugs to power up these new bulbs, which are 35watt bulbs but run on different voltages.
There are many places which sell HID conversion kits for around 300 dollars give or take depending on the company. This is an easy way to add HIDs to your car at the expense of possibly blinding other drivers.
Projectors
To start with, a projector is a different application than the stock reflective housing. The stock housing reflects the light produced by the bulb and aims it through angles and curves in the headlight. A projector has a normally smooth bowl shape on the back side to collect the light and reflect it into a lens, which focuses the light into a more concentrated area. This is the reason that many people are disappointed with projectors they purchase from ebay etc. These applications focus their halogen light into a more concentrated beam, and thus cutting away some of the scattered light so the beam is restricted much more than in the stock headlight housing.There are some vehicles that come with halogen projectors which do a better job than most aftermarket projectors that are produced for the cavaliers.
Almost every high end vehicle that has a HID system, use projectors designed for HIDs. Buying a set of aftermarket projectors and putting HID bulbs in the housings is a risky thing to do as I do not believe any projectors are confirmed for use with HID bulbs, since they produce more heat than their halogen counterparts. There are many different types of projectors on the market and a great site to read more information about HIDS and different styles of Projectors is:
http://hidplanet.com/forums/viewtopic.php?t=2080&sid=b7aacc420b711e031ca672c9414107a5
You may have to register for this webpage to view the forums.
The general link to the HID Planet is:
http://www.hidplanet.com
By clicking on the right hand side you can access the forums.
This webpage has just about any information you will need to ever know about HIDS and projectors.
Retrofitting projectors
I am not going to go into a ton of detail about retrofitting as it can be found on the HID planet forums in great detail, but the idea of retrofitting is to change from a halogen reflector housing, and adding a HID projector, HID bulb, and ballasts.
This ensures that you are not throwing light everywhere when doen properly and can give amazing color output whlie increasing your light output without the danger of blinding other drivers on the road.
In the end, if you are considering purchasing a HID kit to just plug in, consider looking at HID Planet where they also sell full kits which include almost everything except a wireharness to do a projector and HID retrofit into your car. The forums actually have a how to on creating a wireharness for your application, often other users will make them for a small feel, or even point you to a webpage you can purchase the harness through, the one that comes into my mind is:
http://www.xenonking.com
There are a few users on the org who have done retrofits, and the results are amazing to say the least. If you want to attempt something like this, check out the forums, read up a little, and see, for just a little more money than a plug and play HID only system would cost, you can get a kit including projectors which will in turn provide a much better light output for you.
http://www.aplusperformance.com
http://www.modified-motorsports.com