Thank you for your reply and advise PurpleAngel.

Hi All At the moment, I have a Focusrite 2i4 and a pair KRK Rokit 8 speakers. The KRK’s have their own output and are connected to the 2i4 by XLR. Recently I switched to an iMac, and I noticed no difference in the quality of the output of my music collection, which is in either FLAC, WAV or APE...