I had the same speakers. Those things ask for alot of power. I never got mine to sound right for what they are worth. They are sitting in my garage as I type. Not sure what to do with them. Anyway sounds like your amp in the stereo might be going out or getting hot?
Thats funny. I did the same thing last month with my brand new SAX 100.4D. Luckily it still works thanks to the 3 30 amp fuses it has!! I was so out of it, I really thought it was gone. Bought some new fuses and it lit up like a CHAMP!
Well in that pic it looks like mine but mine has the Fi sticker in the bottom. I purchased mine about 5 months ago. But you might have to put more pics of it that show sideviews of the sub.