Hi all I am relatively new to the forums, I am about to get a 2009 Altima Coupe w/Bose and am already planning to get a new HU and add subs. However, I would really like to upgrade the front and rear speakers while I get the new HU installed. My question is will it messup the sound if I just replace the front/back and not the tweeters? I plan to have the speakers attached to the head unit unit and get an amp for them eventually.

What I am getting right now.
HU: Pioneer AVH-P8400BH
AMP:Alpine MRX-M110
Subs:JL Audio 10W3v3-4

If you're going to replace the speakers, you should replace the fronts with separates if it's in your budget. Just putting a coax in there is going to make it sound a little funky.