Sony decks, even ES series... 90 db S/N ratio
Alpine... 105 db S/N ratio...
thats a big factor is SQ.
Sony makes SOME nice looking products, like the MP70... but they really tend to not last. Ive owned a lot of Sony products, and they all just stopped working in one way or another pretty much. I had an older Sony 5 disc home cd player, I went through 4 of them within the first month of owning the first one, all replaced under warranty, but they just kept crapping out on me. Sony reciever crapped out after a year. Sony car cd player crapped out after a year. In my experience, Sony just dosent last. Sound wise, it is ok for middle-of-the-road equipment.
I would really try to stay away from Sony... although the 10gb hard disc head unit is sooo cool, I wouldnt buy their car stuff.
Their older ES equpiment, before the Xplod crap came out, was the best... awesome sound quality, simplistic looks, great features and a great warranty. But even their ES car stuff has gone down the crapper.
I also recomend the Alpine CDA-7894 for a great MP3 deck.
I, personally, think the alpine decks look ok, i'm not too into the really flashy ones... but to me the Alpine decks look good, pretty simple, the only thing I dont like is the typical LCD display... a nice dot matrix would have been nice on the 7893 and 7894!!
If you want flash with good reliability and sound quality, Panasonic is a great brand too!