I got a 1993 Civic Dx 2 dr and i have pioneer head, pioneer 6 1/2s in the doors, 2 pioneer 6x9's hidden in the back dash, 2 pioneer 12" subs in the trunk being pushed by a 800w pioneer amp and thats to much so i would say that maybe a 10" unless u wanna buy an amp then i would say go for 2 10" subs in a Bandpass and those will hit hard enough
Pk

 

lilgreencivic, i will be buying an amp either way....and i wouldn't even consider 2 10" subs. i'm now looking at getting 1 round 10" for the trunk.