Have you settle the pop problem?From my experiance, sometimes its the amp.Have to check if some capacitors burst or what.Sometimes cant do anything with the amp.Just have to life with it.

Check if ur HU also grounded.RCA and Power cable next to each other sometimes unable to avoid.Try using a ferrite magnet and see if got any improvements.

Monster cables got many imitation.If you bought it cheap chances are its imitation.Trying swapping some parts and see which is the culprit.