Bridging Sonic Impact 2 amp

T amps power output

My concern is that the T amps power output of 15 watts per channel may not be adequate for prolonged hi level listening into a midrange driver crossed over at 330 hz with a sensitivity of 91db 1w1m.
I am using a Behringer dcx2496 to cross the drive units over with 8th order Link Riley slopes. By what ratio does the output capacity of an amplifier increase with the implementation of this kind of high pass filter? Is there a graph on an applet somewhere?