You are about on target with the cost per axle assy. However, bad cv joints are more often associated with repetitive clicking or metallic snapping noises. Clunking noises are more frequently associated with differential or driveshaft problems. Swapping out the axles on a 300E is a doable DYI job. Make sure about you diagnosis. $1700 for both seems a bit high. The labor is not complicated.
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.