Go for original equipment replacements. There are a lot of sources out there, http://www.oediscountparts.com/ is a dealer for both Mercedes and Chrysler and has good on-line prices and excellent service (and no sales tax plus free shipping for orders over $50 or so).

As has already been noted, K&N flow well when CLEAN, but if you care about dust infiltration, use OEM quality filters and change them regularly.