kicker is all about loudness..if u want loud get the 12 and with the 8s ud get a little bit better SQ so if ur going SPL then u get on that 12 and ull be set
i have a single 8 l7 right now in a 00 eclipse. its ported and it surprised the h*ll out of me. id say for wow factor and the performance the 2 8's will get loud. but it would be farely close. good luck
a guy i work with has 2 8's sealed w/ a kx1200.1 and it pounds almost as mua bit more than my 12 sealed but im onyl running about 600w to it... both properly powered i think the single 12 would be best esp if your porting.