I have the infinty components set up, low-mids in the doors and the tweets where you want them... but this combo comes with a cross over, and I used it and can tell a dif with-without it being used.
you can have the tweeters play 2 dif ranges, well high or higher+ ranges...
a cross over will send the correct range to the tweets and subs speakers, so its not getting ranges it can't handle.
that is from what I understood from a little online reading.
either way the sound is good, I enjoy good music at normal volumes over loud overwhelming bass and missing ranges... I really like my components up front with 3 ways in the rear with a 10" box in the rear hide away area (home made box)