I work for Circuit City, and played around the car audio department for a while before making my selection. I went for the jewish route, and I honestly, couldn't be happier with my decision. I drive a beater car, and really didn't need anything special, but little did I know just how good my stuff would sound.
Sony GT-120 headunit
2 pairs of Pioneer 4" speakers (TSG1042R)
Sony 800W 2 channel amp
2 12" Eclipse subwoofers (these were an open box set that just got back from service, and I picked up for $31 for 2 subs and a box, don't expect to find that deal EVER).
With all the wiring etc, I paid about $360 in all, and my stereo destroys 9/10 cars in terms of audio quality. You don't need the top of the line for a great sound. The head unit was installed before I put the new speakers in, and the sound difference was a lot bigger than I was expecting, however, I ended up blowing out the stock speakers within a couple days (stock head unit put out 20w as opposed to Sony's 52w per channel). New speakers all around really made a difference.
I did blind sound tests between the $50 pioneers, $100 polks and $120 Kicker speakers, and Pioneers were 2nd place in terms of sound quality to my ears (Kicker = #1, Polk was the worst [I was shocked too]) .
Moral of the story is, I went for the jewish audio setup, and I really concluded that you dont need to spend huge bucks to get great sound. Pioneer makes an excellent set of speakers, and with my low-end Sony headunit, they make an amazing pair. Subwoofers is just icing on the cake to fill out the low end that those 4" speakers lack.
