midbass for front?

Hi right now im running a mp3 pioneer deck with a jbl amp pushing 90 watts rms x 2 to 2 infinity 5 1/4 speakers in kickpanels and I took out the 6x9s in the back so bass can escape through there. Also running a 1000 watt rms alpine amp to 2 12inch infinity perfects. Right now my sq is amazing with crisp detail and amazing lows and midrange is punchy as well because I reinforced the q logic kickpanels cause they make they doodiety. But my question is i have another jbl amp that can push 90watts rms x 2 that I have laying around the house. right now there is no speakers in my front doors. I plan to sounddeaden the doors pretty soon because I have sounddeaden the rest of my car. should I buy another set of the same infinity speakers(6.5inch) to fit the doors and run it off the other jbl amp or will this cause cancellation issues because of the 2 tweeters? Or is there a way I could use just the midrange off the speaker instead of the tweeter since they are not components? I want to get a midrange speaker but in my honda civic the mounting depth in the doors isnt much to fit a big magnet in there. But I know the infinitys would fit. My system is pretty damn good in sq and imaging right now, but I want to find out if adding 90 watts rms each to 2 speakers will make a big difference.

sorry for the long post. help appreciated.