I use Chord cables. In the case of SpeakerLink, their Signature cables - between an 808 and 5200SEs. Quite an expense, but did make a difference and I have no regrets.

When choosing them, Chord lent me a range of cables to try, which I did extensively over a period of three weeks.

Possibly other manufacturers will do something similar.

William
808.6,HD621, Oppo 103EU, DSP5200SEs, DSW.2; 218, DSP3200s, Oppo 105D, Panasonic PVR, Panasonic plasma; F80