Audio help on 91 Sunbird LE

Hey guys, this is my first post here. I got a 4 cylinder 2.0 liter 91 sunbird LE coupe with 180K on it as my first car, and i love it. So far i got a kenwood deck + sony xplod's for the rear speakers, and i really dont like them but i can live with them. Im about to be buying 2 10inch sub woofers and im going to buy some new front speakers. My question is what should I look for in buying an amp, and what size front speakers does my car have? ( i pressume its a 4inch speaker but im not sure)

Thanks,
Alex