Denon DRA-685 & KEF Q9 - Very low volume and tinny

I just purchased a pair of KEF Q9. When I listened to them at the store, they were amazing. Until when I brought them home and hooked them up with my Denon DRA-685, the sound was very terrible, the volume was really low. When I turned the volume up, there was severe distortion. I'm a newbie to the whole audiophile thing. Please let me know what should I do? Should I change my receiver? Do I need an amp or whatever I should do in order to get the best out of the speakers. I truly appreciate your help.