Sound Systems

I prefer the Pioneer head units myself and tend to stick with one that has tons of audio options as opposed to animated screens and color changing lights. Although my next one WILL have HD radio. Speakers: pioneer and sony ( see my setup :) )
Having lots of tune-ability from the head unit can make even crappy speakers sound good. Add good speakers and you've got a nice system that sounds great.
Sound quality is more important than sound volume.

For a neat exercise, go into walmart or best buy, pick the cheapest speaker you can find, THEN try to get the sound you like out of it with all of the different head units...the one that makes the crappy speaker sound good is a decent unit

My current setup is:
Pioneer p-3000ib ( older head unit ) $125 at crutchfield back in the day
5.25 Sony speakers in kick panels $45 online ( powered by the head unit )
6x9 Pioneer speakers in rear deck $50 online ( powered by the head unit )

2 P1 punch 12's in the rear quarters ( custom boxes that are flush with the trunk opening ) powered by an el cheapo Dual 400 watt amp.
Paid $50 for 12's and amp at a local pawn shop.

Add another $30-$50 for MDF and wiring etc.

So for $300-$400 you can have a system that will make your ears bleed.

I might end up changing it up a little because I've swapped in the fold down seat so the 6x9's in the rear deck are in the way. I've been thinking about putting some 6.5's in the rear "door" panels in the front part of the quarter panel and a couple of 4" speakers in the front dash grille. The sound should be a little more precise with more speakers and more fine tuning ability.

The main problem that I have is that because I've hidden everything I've got to drive the speakers pretty hard to overcome their lame mounting location and concealment.