Start emailing companies that make subwoofers, though most of them will only sell complete soft-part kits.
Their issue is according to a few I've talked to, is that if they start selling all the parts separate people become quasi-manufacturers and become more competition for them.
Motors and baskets can be had on the cheap on these forums, I've found a couple places for various soft-parts, Jacob at Sundown has some good stuff but has been a bit slow in responding to my emails, I've ordered some more parts from another company, I'll reserve my review until I get them in hand.
SSackett can get you ish. niqquas sendin me a dustcap on the low. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
alot of companys dont want there parts on another manufactures motor. such as you buy soft parts from x and build off company y's motor and coil rubs or glue looks like ish they dont want to be linked to that...
You just get a subscription of Voice Coil magazine. All the manufacturers are in there. Im not sure how I got a free subscription to it.
For voice coils, none better than Precision Econowind out of Florida. damn near bulletproof coils, way better than the china stuff with the duck sauce.