How does 1000 watt RMS subwoofer Not mean anything thats what the company set as it power rating at all times.
1000W is the thermal power handling of the sub. Take note, that means it's the amount of heat the sub can dissipate before voice coil damage occurs. You can bottom out a sub with far less than 1000W given the right conditions. This is one reason why the amp needs the subsonic/high pass filter set with vented enclosures.
It is never a bad thing to overpower a sub. Your amp can produce 2100W RMS, and I specifically recommended it so it would be difficult to clip the sub with a thermal overload. You would bottom out the sub before you exceeded its thermal limits, and that's a lot easier to tune around because you can actually hear a sub bottoming out, whereas you can only smell a voice coil burning, and by that point it's too late.
I have very rarely seen people blow good subs with too much unclipped power. It's always a function of the sub bottoming out that damages them at that point, but like I said, it's something you can hear. Here's how a sub sounds when it's bottoming out.
Chris, only you would be able to tell us if the sub was indeed bottoming out. Did you hear that sound when you opened the trunk? If you did, and you kept turning it up louder, then you simply pushed the sub way too far.