I have run the Durango with both the 550 motor and the Pro4, currently settled with Pro4 motor. Both were fantastic to drive and plenty of power and torque. The RX8 will power them round all day without issues. If you go the 550 route then go with the 5.5, the 4.5 will just be too much.
Either of the Tekin setup will be spot on so go with what is the best deal
