Please feel free to call me stupid.

I've got my late grandfather's D130 and K140. I have been using the D130 with a Bryston 3B 400W mono amplifier for use as a powered subwoofer. I ran this this way for two months with no trouble, but yesterday I fired it up, and it all of a sudden went silent. I haven't had an opportunity to switch amps, speakers, cables or anything. I didn't smell anything when it went silent. When I turn up the volume real loud I get barely audible sound.

Did I blow up my precious D130, or was it hopefully the amp (which I can fix myself)? Also, if I did blow up the D130, how would the K140 do in its place? I'm using this as a sub, and I've heard that the K140 has better bass response. Help please?