I had a pair of Kappa 572.5cf in my doors and they sounded fine but nowhere near as good as the (cheap line) MB Quarts I am running now!
Infinity was much better than stock for me but nowhere close to what I wanted to be hearing

I cant wait until I find an amp I like to drive a pair of MB Quart separates up front

 

Some like the metal dome tweeter sound, me, I can't stand it. Like fingures on the chalk board.