It doesn't matter if you're clipping the signal or not, if you over power a sub, it will blow. Setting the gains "correctly" won't help as the possibility of overpowering is always there as music is always different. No two songs are the same. If you're overpowering a sub, even with "correct" gains, you still have to be extremely careful. You should never ever overpower a sub unless you know exactly what you're doing, and know exactly what you're listening to. What I'm saying is it's impossible to set the gain to a test tone or to a certain song, and then expect everything else to be exactly the same. Everything is recorded different. You can set the gains to one song, then the very next song with the same gains could blow the **** out of the sub because it was recorded differently. The only way to safely overpower a sub is to "idiot proof" the settings by setting the gains with everything (volume/bass/bass boost/loudness) cranked up so that the signal can never be overgained, which results in crap sounding mids/highs and/or low bass output from the sub.
I'm pretty sure the Orion XTR subs are very overrated, so are the cheap Pioneer champion subs. The GM-D9601 will put out 1200rms, never go by the maximum rating. The Pioneer champion subs I believe are around 250rms, orion XTR PRO's are 600rms, so it's no wonder they fried.
The people here will make you think you can put a 5k amp on a 250rms sub if you just "set the gains correct" but it is simply wishful thinking and doesn't work in practice. I've seen it happen 3948759038476984769842 times, **** will not and does not last because eventually you'll play a song with higher bass levels, or you crank the volume one notch too far, or somebody turns up the bass, and fries your ****. It's not always distortion or user error. The biggest error is installer error by improperly matching an amp to a sub.