well i have one fifteen in the back seat. this is temp. later i am going to put two platinum 15's //content.invisioncic.com/y282845/emoticons/clap.gif.178cba2c538c68e720c727fcb024b19c.gif ported in my stang. i never heard an XXX so i cannot compare. but i did heard a w7 in a showroom. it was loud but in a car it will sound different. i the only thing i can compare them to is two L5 12's in 1.5 cubic feet box, four audiobahn aw1200Q in 1.2 cubic feet sealed box and two ported aw1208t. from my personal experience i thought that one fifteen in a 4.5 cf box got louder that all of them. plus they are rated at 1000 rms and i am giving them 1500 rms at full power and it takes it like a champ. you should try digitalgiftworld.com i think thats it. they got them for cheaper but no warranty. i was surprise how loud one got. //content.invisioncic.com/y282845/emoticons/scared.gif.f134e57c6c93ccd0f15aa5ac32c7d4a0.gif . i paid 290 for both.