I was wondering if there was a big difference between the Infinity Kappa Perfect 6.1 and the Kappa Perfect 5.1 speakers? The installer said he wouldn't install a 6.5" component set in my car but he could do a 5.25" because I have 6x8 openings in my car. So i was wondering if I should just let him do the Kappa Perfects 5.1's or should I try to find someone who will do the 6.1's?