The best location for speakers is the stock location. This place gives the most equal distance from each speaker to each ear. If the speakers are above your head, you end up with one speaker right at your head and the other is a couple feet away. Buy a 5 1/4" components set and install in the factory location or in the doors near factory location. These sets are the best way to go for sound quality. Buy the most expensive set you possibly can, you really do get what you pay for! I would not even bother with the crappy oval speakers if you are going for sound quality.
Save that money and put a decent amp on that component set! If you have not bought the head unit yet, get one with the highest preamp output voltage. This setup will create the brightest highs you have ever
heard and you will hear small details of the music that you never knew were there! Before you buy any amplifiers, check out US Acoustics. These amps have the same THD and power output capabilities of other brands that cost WAY more.
http://www.usacoustics.com/