never seen a 18w3 perform very well. i seen a pair walled in a civic barely break a 140. it was a very crappy install though. but im sure they perform good for their power handling... i dunno
then again, at the last competition i went to, a cutty walled with 2 18" MA audio HAD to bassrace the 129.9 class cause he barely broke 132 about 20 seconds into his run LOL //content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif
it can definetely come down to the install, make ya or break ya