First, the upgrade/mod for the door speakers is for addition of capacitors. Not resistors. I hope this helps?

Second, I replaced the 6.5" door speakers with a pair of Infinity speakers:

Amazon.com: Infinity Reference 6032cf 6.5-Inch, 180-Watt High PerformanceTwo-Way Loudspeaker (Pair): Electronics: Reviews, Prices & more

these made a great improvement in the mid qualities.

good luck!