I recently put an Audioquest Diamond USB 3.0 cable between a Seagate external drive (housing 24 and 16 bit FLAC and ALAC files) and a Cambridge Audio 851N streamer and was amazed by the results. There is no other way to put it other than that the sound came alive in a way that I had never heard from my system before.
The Cambridge streamer is connected with Kimber Hero XLRs to my Mac pre-amp, which in turn is connected to a MAC solid state amp with more Kimbler Hero XLRs. The final connection are Audioquest Rocket 88s speaker cables to a pair of B&W 702 Signatures.
I thought the system sounded great until I swapped in the Audioquest Diamond USB 3.0 and all of a sudden I had a brand new stereo system. The experience made me realize how much difference one weak link in a system can make.