This is just a quick Comparo I have experienced... It may not be the same for all but I thought I would share my discovery with you..
My Magna came with the Sony Headunit already installed and connected to the Stock speakers, Which I then changed out for a Set of Clarion Splits and a Set of Eclipse 4-way 6x9's.
The person who installed the deck made a butchers of the wiring.. and a mess of the dashboard.
Which was part of my inspiration to re-wire the deck.
Since I no longer roll with a Sub in the boot.. I decided to install the Old Pioneer deck from my long gone Vitara..

I originally had a Sony CDX-GT250S
http://webstore.cde.co.za/Products/67/73343.jpg
52W x4.
MP3/WMA
Selectable Subout.
I replaced it with :

The Pioneer DEH-2950MP
http://www.e-brothers.jp/images/DEH2950MP.jpg
50Wx4
MP3/WMA
Rear RCA only.
The Pioneer DEH-2950MP is the Entry level MP3 Deck from around the same era and I have to say..
Sounds far better.

Since I am just running Splits and 6x9's straight off the deck with no amp the Improvement has been phenomenal.

The Old Sony Deck went loud and was clear but never really made the 6x9's or the Splits deliver the punch needed... the sound was sort of, well, Flat..
The Sony Deck had Level adjustments of Bass, Treble and Mid... with a Selectable sub out but no Loud button..

After I had installed the DEH-2950MP the Eclipse 6x9's regained the punch that 6x9's are known for, the Splits that had once felt like they were out of Phase, now sounded full bodied.. I had previously rewired them twice with the Sony Deck to make sure they were not out of phase, which made no real impact. The Loud button really made the difference..


Now I am not putting Sony down, or Making Pioneer sound like its the bee's knee's but I cannot help but express the difference the change in decks has made..

Now I realize I no longer have a Sub out for when I want to put a sub back in, but to be honest... with the way the system is sounding now, I don't think I will be..

I work at JB hi fi in car sound, and i have compared all decks

Pioneer decks do sound the best, are easy to tune to make speakers sound good off the deck,

i had a pioneer in my first car, then got a jvc , and then bought a pioneer again..you can't beat the sound, other decks don't compare!

Alpine are good, but pioneer have LOW MID HIGH Loud settings which makes it easier compared to just the LOUD on or off!

I used to run pioneer gear in my car and have converted it to all soundstream. I love the sound of the speakers but I don't think the soundstream HU is as good as my old pioneer. Think I might look for another pioneer HU to put in.. I agree, pioneer are very nice :)

I work at JB hi fi in car sound, and i have compared all decks

Pioneer decks do sound the best, are easy to tune to make speakers sound good off the deck,

i had a pioneer in my first car, then got a jvc , and then bought a pioneer again..you can't beat the sound, other decks don't compare!

Alpine are good, but pioneer have LOW MID HIGH Loud settings which makes it easier compared to just the LOUD on or off!

Thats a little bit vague to say 'I work at a store that sells a few brands, therefore I know what the best of the best is'.. Its the kind of comment that leads to people reading it, taking it at gospel, telling friends, and it starts to balloon and you end up with an industry full of incorrect information.

Trust me, if you are saying that 'low mid and high' settings make for a superior deck, then you have a lot to experience... most of the top quality gear you would never see in a JB Hifi store, and most people have never heard of.

To the OP, what is really amazing is that you could get that same improvement in sound over the Pioneer if you were to put in a better head unit still. People really underrate how much of an impact a head unit has on their system, and its great to see that you have your own proof of that.. there is only so much people can tell you before you have to experience it to believe it :)

My car came with a pioneer headunit and i presume pioneer speakers.. I haven't even checked but they certainly are not stock and sound brilliant!

You want an improvement try running a Kenwood entry level deck and then swapping that out for an Alpine 9887 with Time Alignment. I made a mess of myself at that point.

I really rate pioneer gear, but as Woob said, theres always better gear out. For entry level shit tho pioneer is pretty damn good. Love the sound im getting from my speakers straight off my pioneer HU

I'm really fond of the Pioneers, seeing I'm a cheapskate and buy second hand radios for my cars at $50 each. lol Both so far have been brilliant, especially good is the ability to adjust the sound cut/boost etc so that any crappy set of speakers sound good, in both sedan and wagon. Sony was tried in the wagon before the Pioneer with the same speakers but sounded flat no matter what, so it was junked. When I get really financially reckless, I will buy a NEW HU with all the features, and it will be a Pioneer of course. lol That's not to say there are no other good brands out there of course, but between Sony and Pioneer there is no doubt the Pioneer is better.

I know that it would sound better with a more expensive headunit but as a basis of comparison between entry levels of the same era, and the same Price point, the Sony did offer more features but its the sound quality I found lacking in the Sony, that seemed to be in the Pioneer..
As I said in the Original post, It may be different for others, but as a comparison with the decks I had with nothing more then a swap in, swap out situation without any added technical amplification or Signal processing, the Pioneer came out audibly better.

I am pretty certain that if I was to use an Amp, I could possibly run into a clipped signal situation with the Pioneer deck which I would not have with the Sony but as far as direct Headunit sound quality, the Pioneer (for me) has the Sony beaten..

We are all agreed then. lol

Im not 100% but I think you will find that the reason the Pioneer sounds better, is because it has filtering that cannot be turned off, a lot of amplifiers come with these attributes, they basically modify the output, much like a 'loudness' feature on a deck would, to a lesser extent, to appeal to what the manufacturer expects its buyer to like.

It works too, here you are raving about the increased quality :) I doubt that is the whole reason however, I expect the Pioneer probably has better damping properties and whatnot which gives much better bass control through your 6x9's among other things.

Same headunit as meh! I like it too, just wish it had usb.

Wow.. it wasn't just me...
I took a couple of mates to Wollongong today and they complemented the difference.
According to one of my mates (who is not very good with technical terms) just said the Lows were lower, and the Sound more crisp..From the back seat he actually thought I had put the sub back in...
till he remembered that he had just chucked his bag in the boot
and it wasn't there..

i find jvc headunits work very well depending on what u buy to compliment them. my jvc rd 406(i think thats the right one) has great sound quality when used with complimenting jvc coaxials front and back. very clear sound and delivers right bass levels. i also bought a jvc amp with an alpine type s subwoofer and the sound quality is very good for a budget system