about Magnepan and power

Much has been written about how the Magnepan speaker needs a good jolt of power to perform at its best. My question would be is this a speaker that has no limits? I'll refer to the 20.7 seeing as this is the model I own. There are no power handling specs listed like you would see in many other speaker manuals. They're driven by 1000 watt amps. They can get pretty darn loud in my 16'x24'room. I realize that there is a point where too loud gets uncomfortable. When can it get damaging to the speaker? Ok,I guess that's two questions. I should clarify, I don't make a habit of listening to music at ear bleeding levels. It's more about those pieces that have softer sections that you tend to turn it up a bit and then have to hit the volume button when the crescendos hit. I have had the 3.5, 3.6 and the 3.7 before these and never damaged a speaker. So, what are these speakers limitations?