I've got an old set of the Kappa 6.5" components in the front and they fit perfectly, even the tweeters. You just have to carefully drill out the weld spots of the old speaker and reuse the mounting ring. Unfortunately one of my tweeters has blown, though I'm not sure it's my fault.
I would think I'd be deaf if I had pumped in enough power to fry a tweeter before the woofer.
My Kappa Perfect 10 VQ from Crutchfield should be arriving tomorrow!
I would've gone for the 12" if I had an enclosure handy, but I've already blown enough money recently with a Pioneer DEHP770MP and a Rockford Fosgate DMP1.
KuoH