I hope I'm wrong on this, but the laws of physics are hardly bendable..
Oh so true...
As much as we would like them to be, they are not.
Just because a sub can hit 10hz does not mean it will do anything better than anything else out there. It will totally depend upon what SPL it can generate that low and where that SPL is relative to its average output.
Every sub I own hits 10hz, it is just so low in SPL and frequency that I can't hear it.
Back to the topic at hand, I think Mike C is correct on his assumptions about what they replace/how they compare.