i install audio equipment for a living. so i can help you out if you have any troubles. is you civic a hatch and coupe?

hatch - just have to pop off speaker covers and take out screws. depth is not an problem

coupe - must remove the whole rear deck cover, might have to take out part of the seats. depth of speaker is also not a problem

i would suggest some rockford fosgate power series 6x9's. you dont need a amp but they would sound alot better with one.