Do they smell burnt? Every time I have blown mine there is a distinct smell, and then they start to make that plastic like sound you were describing.
I had a set of the Audiobahn woofers they were great, I didn�t blow them. I just wanted more trunk space, so I bought some eclipse 10". They are in a 2'^3 box. The eclipse 10's have deeper bass and sound more clear, but they don�t have the air movement like the 12's I think if I had more power they might be about the same. My friend has the Audiobahn woofers in his car and they are still going!