I have a 2003 also but I wanted better air filtration than the standard filters because of the air quality here in the Washington D.C. Metro area.
Anyhow, I made my own three-phase electrostatic filter from scratch. Its not hard to do and it works *really* well--maybe too well; it actually took out the "new car" smell. :-)
As a side benefit, the electrostatic filter is a 'permanent' filter -- it is
*designed* to be rinsed and reused. That is, a person only buys one per car, ever.If there is any interest I could post construction plans.
- Mike