A few people here including myself have purchased a
HID conversion kit from DDM Tuning and only cost $29.99
I really don't believe you can beat the price & quality, IMHO.
Many people say that they don't want to convert the high beam
lights but I think to keep the look constant throughout I would
change them also because the cost is so low.
Here's their site: Apexcone Raptor HID Kit (35w or 55w) - DDM Tuning: HID Kits, DEPO Lights, BMW Bumpers & Lighting - DDM Tuning

Introducing the Apexcone Raptor V2 Mid Sized HID kit.
Apexcone Raptor V2 Hid Kits have the same width and
length as its' predecessor, but are 3/8" thicker. These
full size ballasts are nearly bulletproof; bringing reliability
and value in one. Due the the improved reliability, we
are able to offer a FREE LIFETIME WARRANTY on our
Apexcone Raptor V2s!
What is the difference between 55w and 35w kits?
Our 55w HID kits are 40% brighter than the standard
35w kits. The 55W system ballasts are about 1 cm longer
than the 35W ballasts. 55w kits tend to wash out some
of the color of the HID bulb due to the light output
(for example, a 55w 8000k will look similar in color to a
35w 6000k kit). Our 55w HID Kit is not recommended
for smaller fog light housings because they tend to
concentrate a large amount of heat in a small area.
HID kits for the price of a pair of super blue bulbs?
Of course. Value is what we are known for.
We can price these so low because they are made
in a factory we have partial ownership in. We don't
pay the factory a profit, we can pass the savings on
to you.
Each Kit Includes:
- 2 Fullsize Raptor Ballast
- 2 HID Bulbs
- Free Lifetime Warranty