I bought Denon AVR 2106 2 months ago online (bigondigital) for $500 and connected to Klipsch Cinema 8 speakers when I watching certain DVDs the voulme drops down suddenly and comes up after a while or else I need to increase the voulme I used the auto calibartion for tuning the speakers ( this is my first reciver ) Any Ideas whats going on with my receiver ? is there some thing wrong with my tuning ? thank you guys for any info