im a huge A7X fan, but i am really disappointed with the way they sound on my system. i just had my first system installed, two sets of pioneer ts-c160r component speakers, alpine type R 10" sub, alpine 9856 receiver.
my sub doesnt make a sound when the rev (the drummer from Avenged sevenfold) goes at it with his double bass skills.
however, atreyu's (a band i like but not nearly as much as A7X) double-bass lines make the thing boom.
as a drummer of 15 years and a drum teacher for roughly 5 (im only 24), i cant figure it out, because they both have similar sounding kick drums live, and ive seen them both like a combined 25 times.
the way the recorded the new avenged sevenfold album, there's no deep bass at all really.
try "the grand conjuration" by opeth, "where do u draw the line" by From AUtumn to ashes, or 'five vicodin chased by a shot of clarity' by atreyu, esp the end of the song