Planning on putting a decent system in my old truck and could use some simple advice/guidance!

Alright, so I consider myself somewhat of a music connoisseur and that has led to me being an audiophile. I want a good overall sound experience, but I don't know what "specs" to look for besides reading reviews on products. I am a quick learner (EE student as well,) but I know close to nothing about car stereo systems and what the terminology implies (watts, channel, amps, component/coaxial speakers, ect) in sound quality sense or what you need to have for a high quality sound.

So, I would appreciate some advice on the basics of having a full audio experience in an old truck. My truck is a 1997 Dodge Ram extended cab, and from what I can tell it has four stock speakers. I put a Sony stereo in the truck about two years ago. I am guessing its the basic 52W x 4 (also don't know what this implies, im guessing 4 speakers with 52 watts each max?)

Before I begin, being a student, I live on a tight budget budget. This affects many of my decisions.

To start , I figured I should replace the stock speakers first. I read reviews about the Sony XS-GTX6931 speakers and figured they would be a good choice due to price/quality ratio. I got confused with the names of speakers and their importance (component, coaxial, ect) though. What would the four speakers in my truck be called? Is it common for a pair of different type of speakers (one each) to be sold, because that's what I am seeing? Do you buy one for each side of the truck? I also found an old amp in my brothers truck (Rockford Fosgate 250 aII) that I could use (does this improve the sound quality, I don't care about how loud my system is?) It is a two channel amp, what does that mean in regards to the number of speakers in my truck? Also, I listen to mostly country and music lighter on the bass so I wasn't planning on a sub unless it would really help.

So, if you car enthusiasts could point me in the right direction to a decent sounding system with the supplies I have, I would greatly appreciate it!

P.S. Would having a "tweeter" speaker help, and could it be added to the other four if the radio is only 52W x 4?