Volume knob on receiver still needs a bit of turning. Amp needed?

My Cerwin Vega D-9's rolled in yesterday and they are big EFFICIENT floor speakers. Each pair has a 15" woofer running @ 200wattsRMS/ch(400 peak). I'm powering them with a Yamaha 7.1 ch. receiver giving them 105watts each. When I tested these at the shop, the volume knob only needed 2 inches turning to be loud WITH "great" b. At home on receiver, they go VERY loud as well, but needs like 6-10 inches turning WITH only "some" b. How do I make these speakers have sensitive b and loudness? I need to drive the subs man!