dude your front speakers arent that great should have gone in for 1061 in front.its normal for the sound to crack at a certain volume.that happens in all speakers.
yes the sound does get slightly muffled with the tray on top and it would have been better if you attached the speakers to your tray itself.
pioneer yester year originals had a code number printed on the magnet where as the duplicate ones didnt.
By the way guys be really carefull just heard from a dealer that a consignment of fake JBL speakers along with some other fake stuff had come down from dubai and the quality is so good that you cannot telll the difference except for the grill plastic rim colour which is silver on the duplicate ones.