Need a new stereo

Ok guys and gals I need a little help here. I have a 1989 ford ranger 2 door and i have a total of 1 speaker working and it sucks.:headshake Im looking at getting a new stereo system Im wanting to replace all 4 speakers. I went to a website that says I need 5.25 all around. I also want to go ahead and install a new head unit while im at it. I dont think I will be purchasing a sub as my music style doesnt really need one (classic/some hard rock) i dont believe. Please correct me if I am wrong. Im looking for something AFFORDABLE. Any suggestions?

p.s. I did read the noob audio post

Also if i buy 4 speakers and no subwoofer would you suggest an amplifier?

I always suggest an amp for speakers, also you will need at least a 10" sub. 5 1/4 " speakers will not have much below about 100 Hz Try looking thru crotchfield for a good model, then find it cheaper somewhere else.

How can I fit a 10" into my cab?
Would a shallow mount fit behind the seats?
I think i could prabably put the amp under the seats so that shouldnt be that hard.

most truch boxes for non-extended cabs are a small wedge shape that goes behind the seat. A 10" sub should only need about .5 ft^3

Thank you very much.