It is extremely hard to tell true audio quality with the stock speakers. They suck, no way around it. I have found that the audio quality given the limitation of the speakers, interior noise etc has been good when you tweak the EQ settings on the head unit and tablet. I don't have any major complaints. I consider myself extremely picky and the sound quality is just good enough to live with.... Right now.
This is more of a test to see of you can actually get a tablet working for most of your day to day needs without any major tradeoffs.
Here are the specs:
http://resources.jvc.com/Resources/00/01/53/15347.PDF
The thing is, this build is about trying to put something together for under $500.
If you want audiophile quality sound, it's going to put you over $1200, with something like Audison, amps, and Speakers.
And I may get to that point, or at least start with speakers and MAYBE a small sub.