Question about HF drivers and power rating.

[HRobert]

I need help with regards to HF drivers and how the power rating is determined.  Since low frequencies are the enemy of HF drivers, is the power rating for a particular driver based on the lowest frequencies that the unit is rated? Or, is the power handling capability rated by some other factors?  If you cross over the driver at a higher Hz. than it's lowest frequency rating, will the driver handle more power?

Ex:  I have a pair of Yamaha H4201 horn drivers.  Frequency response is 800 HZ to 20K Hz and they are rated at 20W RMS.  My question is this;  If I were to use these in a system and cross them over at 3K or 4K. - far above their lowest rating of 800 Hz - will they handle more power than that factory rating?

Rob