The green Sound Improvement Disc makes a noticeable improvement in the sound from a CD,DVD, and Blu Ray disc . If you can try trimming said discs with a CD edge trimmer like the Audio Desk Systeme lathe you will hear another level of improvement Not my opinion alone .
The edge trimmer also seems to slightly help video images , but not enough to make that a reason to buy one . They are over-priced new , IMO . Got mine used .
Most everything else has been mentioned here by others . I did build my own power cables using Oyaide Black Mamba 12 gauge for the equipment ( as short as possible) and Oyaide Tunami 10 gauge from the wall to the balanced AC power supply with gold plated copper connectors all around .
The edge trimmer also seems to slightly help video images , but not enough to make that a reason to buy one . They are over-priced new , IMO . Got mine used .
Most everything else has been mentioned here by others . I did build my own power cables using Oyaide Black Mamba 12 gauge for the equipment ( as short as possible) and Oyaide Tunami 10 gauge from the wall to the balanced AC power supply with gold plated copper connectors all around .