Be sure you know what kind of auxilliary lighting you're looking for.

Foglights spread a low even pattern of light around the car, and the best ones provide nearly 180-degree illumination, great for seeing around corners at night.

Driving lights come in two flavors, for use with low beam or high beam.

A good resource for information is Daniel Stern's automotive lighting website, http://www.lighting.mbz.org. The FAQs are very informative and I urge you to visit this site.

To visaualize what the dirrerent lights do, you MUST check out the light tunnel feature at http://www.hella.com (on my mac, the direct link to the light tunnel is http://www.hella.com/produktion/HellaPortal/WebSite/Internet_en/ProductsServices/ForDriversAccessories/ForDriversAccessories.jsp )

There are many solutions that can greatly improve your lighting without the expense of HID conversion. For example, I upgraded to E-code lenses (required for HID anyway), Philips VisionPlus lamps, and various modifications to my stock Volvo foglights. Massive improvement. On all my other cars, I've installed Hella's impressive MicroDE foglights.

You could convert to HID but personally I'm holding off as I expect prices to drop considerably over the next couple years. Keep in mind, better performance lighting works best with E-code (euro) lenses. Some later model bricks have a hybrid E-code/US DOT configuration which I expect will be OK. Look for an E in a circle stamped right on the headlight lenses.