I asked the same type of questions about a year ago and got limited responses/flaming. Most of the stuff really comes down to what fits, what requirements do you have etc.
Being a Regal owner, I could fit a double din. Therefore I concentrated there, picked a price range of $400ish and came across what I think is a nice Pioneer with touchscreen. This works out nice because I also wanted a back up camera. Nice big picture.
From there I chatted with a bunch of buddies and they mostly suggested Boston Acoustic speakers. Having the middle of the line speakers, it's amazing. I've never been a fan of super expensive because I don't "hear" the difference personally. Then for an amp, needed somethign taht wouldn't take up the whole car. For me keeping the car/trunk etc functional is a big thing. Got the GTA-1005 amp, it takes care of all the speakers and had room to add a subwoofer. Why not add a sub I said. Got the G3 10" Boston sub.
To me.. it's the best system I've had. To others.. oh wait, I drive this car.
