check the link in my sig for TCON custom subwoofer - i built this myself a little more than a month ago
anyways. mine was a tc9 motor with SSA Icon soft parts and it worked out extremely well, i couldnt be happier to be honest. there is some lead slap but thats easy to fix. so you get a motor and find out the voicecoil diameter and look around for recone kits that are the diameter. once u do that, make sure the voice coil isnt too long or short for the motor you have, so you can optimize the motor's potential.
then you just put it together, not hard at all.