Put co-axial 6.5s in the doors, they sound much nicer then 6x9s. You could also put in a component set, 6.5s in the doors and put the tweeter on the dash or glassīem to the triangles that cover the mirror mounting screws. Then you could put a 10" sub behind the seats. That way you have the low down from the sub, the punchy sounds from the 6.5s and the highs from the tweeters.
Now you can have your tweeters pointing at your head, that way you wonīt have your knees blocking the highs. You can put angled spacers between the 6.5s and the doorpanels, point them towards your head. The 6.5 offer punchier sound than the sloppy 6x9s. You also have the crossover that splits the frequencies between the speakers and tweeters so they are not trying to play sound that they canīt produce. Then get the 10" to cover the lower frequencies.
I also recommend putting something like Dynamat or something in the doors to get much better sound from the 6.5s.
This way you have a nice sounding system so you can listen to most types of music with good sound quality.
Do it once and do it right, rather then slapping something together and wanting more later.