Distortion and popping from new speakers

I have a problem and need some advice. I just purchase a new system from Audiogon members that now consists of new Opera Quinta speakers, a used Musical Fidelity 3.2 Int. Amp and MF 3.2 CD player. Also purchased Purist Audio Vesta speaker cable, Silver Audio interconect and a Zu Cable power cord. I have listens to the new system and it sounds good EXCEPT when I turn it up to about 45% power or about 11:30 on the volume knob. That is when the speakers will start distorting and making a popping noise, I just turn it down below 11:00 on the volume knob and it sounds good again. This is not normal is it? I have tried different CD players, interconnercts and music but that doesn't change things. What should I try next?