Old thread yes, but here is some info I gathered because I had the same issue.
I had the pleasure of the wire breaking right at the cone, soldering works but its not permanent. I added some weatherstrip adhesive so i'll see how that works, but I doubt it will last long. 1st solder job held up, but I turned on some Ludacris and less than a second later the solder broke. LOL! So see how it goes this time....
But some info to add......
The speaker is 120w max, 6in and 2.5in deep.
Using that I found these
So want a permanent fix? How does $15 sound? LOL. The companies arnt great, but then again this isnt a very high end subsystem. I couldn't find any subs from decent companies in the right size/watt/depth. Unless you wanted to try a component speaker in there.