I do stand corrected. Ignore last post, there is a difference but not major. But I guess when it comes to box dimensions/tuning and all that it will make a difference.
i have a single 18 hdc3. 5.6cu its below the window a lport. im doing a 145+ playing music. i think the last time i burped it was like a 146.8?? i think and it was on 2krms
you can get 8 cubes gross right at window line in a 2 door. I had 2 10's doing a 149.2 legal in that space. IMO not enough room for 2 18's. But 1 18" in the right box can get you high 140's on music.
I've got 2 15" woofers in my 2000 4 door blazer below the window line. With batts, amp, etc 8 cubes is REALLY pushing it. I've done 154's sealed at the dash. Hope that helps.