No, the better speakers should always be in front. It sounds weird coming from the rear, when you listen to music at home, or at a concert, the sound is coming from the front. Its called a front soundstage. Most serious sound quality competitors ONLY have front speakers or a "front stage", and if anything is in the rear, its called "rear fill", just some speakers with low power or only playing certain frequencies.
Kappa is usually the better of the infinity brand, but either way will work. Just a few weeks ago I had to drive for awhile with 2 front stock speakers and 2 rear JL coaxials. It was KILLING me, that I could mostly hear the back. Music is supposed to be heard from the front....