I am new to the Polk world, just picked up a pair of like-new SDA-2A speakers and have some questions on them. What is the rated frequency range that they can reproduce? I.E. 20hz-25khz? How much power can they handle? I.E. 200 watts, etc. ? I have a borrowed Sansui 6700(I think) 2 channel amp that powers them, but shuts off around 50%. I'm guessing this is due to too much power. Any suggestions for a newb?