Not important ! Among the early things I did is upgrade the speakers and some six months plus later changed out the head unit. You have to do what works best for you (otherwise, what's the point in owning the car???). At the same time, I agree there are many OE car audio systems that sound worse than the xB2! Have fun, Dude -- don't sweat it, but remember to leave room for unexpected responses !

 

If you don't like the sound, change the HU, run some components off an amp, and there, better sound (hopefully).

 

Just stumbled on this thread , i know this thread is a few years old, but for the sake of just some info. I'd like to add something quite unique with Pioneer's stock Radio for the Scions from 2003~2006
Well first I wanted to mention the different high end Aftermarket navigation Units I was using, I had tested a clarion NX-700, a Kenwood DNX-9990 and a Pioneer AVIC-940BT, All of these excellent units had one draw back, the built-in Amp distorted at its maximum peak naturally.
While Scion's OEM Pioneer Stereo carries an amp similar to the aftermarket amps above, heres the difference between Scion's OEM stereo vs the aftermarket decks.
Ive noticed that the OEM unit does some serious signal processing before the sound reaches the amp. There is some compression/limiting going on before it goes to the amp stage. As you increase the volume, you probably notice the high frequencies and low frequencies changing its values as you keeping turning it up. Pioneer basically designed the unit this way to reduce distortion at higher levels. By the time you get the system at its full volume, you probably are hearing the music with the bass slightly lowered and trebal reduced as well, but not as much to degrade your preference in your sound. The end result is you have low distortion at its highest volume. I actually prefer this method if you decide to stick with your internal amp and not using an external amp.
The aftermarket head units usually have a good amp design with no signal processing other then the standard equalization and loudness. With loud volumes, the amp will produce high distortion based on the principal of Total Harmonic Distortion. So at lower Volume levels, you will get the true values of your equalization settings at any volume. The downfall is at high volumes, the consistency of the equalization is defeated by the distortion.
This is where the Scion OEM Pioneer stereo takes advantage, where you are able to increase the volume and as you increase the volume, the limiter processor inside the stereo automatically adjusts itself according to levels your are playing your music. The result is lower distortion levels.

Any of the Pioneer OEM stereos from 2003~2006 doesnt sound bad at all! As a matter of fact I think it sounds better then many entry and mid level aftermarket car audio products. The OEM stereo's made for the newer Scions were better in terms of features like Navigation and input/output devices but the amp stage were a little less powerful then the earlier Scion OEM stereos. I believe the 2003~2006 delivered 200W OEM power vs 2007~2012 came with 160W, maybe because they figured you could hook up an amp with its RCA outputs.
True enough, aftermarket speakers will have better improvements, but I believe you must spend that extra coin about $500 or more to get that real sound you want out of your music.

 

What ever Scion puts in the cars is not bad, but just not a good investment. Figure you're paying 2x for a factory upgrade as a good aftermarket HU goes for. As to speakers, stock is okay, sorta. But speakers are the ONLY thing you actually hear in a system. Again, aftermarket speakers are the clear winners; they simply sound better.