Anything small enough to place on the dash is going to sound just as bad or even worse than blasting the sound from far away speakers. Not to mention decent size speakers will be pretty large and block some of your view out the windshield!
I have personally listened to car stereos which had indash mounted speakers and I can tell you honestly YUCK. The indash speakers have no real enclosure which made the sound tinny and shrill and distorted badly on the bass notes.
How about looking at your doors? Does it look like any speaker grills are present in the doors..
How about the kick panels near your feet, could you surface mount something there without it making your feet cramped?
Perhaps headrest speakers? You can getaway with rather small speakers if they are close to your ears.. Kind of like using headphones which have extremely small speakers only instead of headphones on your head they are mounted to the headrest..
This was a popular mod for 90's Miatas and you can see an example of a typical install for them
HERE
