I love my x's too! After i got out of class, and borrowed the $45 bench fee and dropped my kenwood amp off at the shop, my little bro and i played around with the x's and some test tones.
I've got 1000 rms running to each sub, each have 2.0cf and are tuned to 30hz. 35-50hz are BEASTLY!! I looked up and saw my sunroof had a good 1.5-2 inches of flex going on, so i reached up to close it, and it WAS closed!!! These things are disgusting on low notes! I'm def. in love, and i haven't even broken them in yet, i've got my gain set nominally, but turned the sub output on my headunit down to 0 again after i set the gain, and they're still ridiculous.
30hz needs some work, i didn't realize how hard it is to set your subsonic on such low notes, they're nearly innaudible, you need to look at your shirt blowing around to see if they're playing //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif