i have 4 12 inch hfi12d4s in my 1999 civic 2 door coupe and its fairly loud. 141db on a hifonics zeus 2000 watt amp and only 4 gauge running to the back on a ghettto box me and my bro put together one night thats half ported half sealed box lol. with a good tuned box and extra power cause my voltage drops way hard i think ill be in the 143 range give or take some. which is good for $30 subs if you ask me. and the sound quality is actually really good. but they wont hit the lows hardly at all. but its all for sale if you wanna buy it