One of my buddies just bought some about 2 months ago and has already gone thru 2 pair(4 subs). Yes they were installed professionally and no he doesnt have a huge amp, they just keep seperating at the voice coil. Seems faulty and a problem with production so just be careful and buy them somewhere that offers full warranty like Best Buy or a large audio store. They are good brand, but have fallen off a little in past years, still respectable for the money they cost. Hope that gives you a little more insight.
90 Kandy Apple Red 300ZX N/A YEAH IM A N/Aer NOW SHOVE IT!