Adding Tweeters

I currently have a pair of the Infinity 600si, the shallow mount 6 1/2" 2 way, speakers in the doors of my 1991 Ford Ranger. In the back I have the Infinity Kappa 5x7". I have a four channel amp laying around that I was thinking of hooking up to them, but also kind of wanted to add some tweeters and an eq. Would I have to run the tweeters and the 6.5's off the amp, and leave the 5x7's for the head unit?

if you just add the 4 channel amp to the existing speakers in the car you should get a lot better sound quality out of your system. i personally am not a fan of just adding tweeters to a system(it gives it that eye twitching super high pitched squeek that i hate). if you do add the tweets, just run them paralell with the fronts and make sure you have about a 2800hz cap in line with them.