Dynaudio C1 II owners - how loud can you go?

Hi All,

I just had a question regarding the review of the Dynaudio C1 II's here: http://www.tonepublications.com/review/dynaudio-confidence-c1-ii/

Jeff mentioned that with the right amount of power, the speakers never run out of headroom. I bought a pair last year and connected them them to a Peachtree Nova220SE (class D - yes, but it's rated 350w at 4ohms). I download and stream a lot of digital music off my mac with itunes+amarra or via tidal, and this amp made sense - I listen to this setup in my bedroom and don't have a lot of room for separates.

My question for the forum is, do these have a problem when playing loud? I can't seem to get more than 10-11 o'clock on the volume control on the peachtree with bass heavy tracks before I hear a high pitched "pop" (almost a bird like "tweet") and have to lower the volume. Does anyone else have this problem? If so, were you able to correct the problem by swapping amps, cables, etc? Am I just expecting too much from these speakers?

Thanks,
Derek