I have Infinity Refs all around...6 1/2's in the doors and the 6x9's in the rear..the fronts had been done previously so I lucked out..perfect fit..as were the rears..I would be concerned about the shear size of the Kappas...they are rather portly in the rear..not a bad thing but limits the space you can put them in..maybe custom brackets and some mods will do it..plus you need a good place to put the crossovers..I love Infinity as well and esp my alpha home spkrs ..keep me informed on the project and if you can make the Kappas work..I may just upgrade to Kappas later