I have the Reference 3 ways in my 2005 Ram QC and they fit with just a little modification(take the plastic spacer off the stock speakers and put on the Infinity speaker). They sound fantastic but they could use a little more bass so I may add a sub woofer at some point. From what I have read the Kappa series 6 x 9 will not fit a Dodge door without modification to the door panel and a lot of custom spacers.
The Kappa is supposed to be better at Bass and handle a little more power but they are less efficent so they require more power. That coupled with the modifications required is why I chose the reference series.