Cable suggestion

My set up is:

PC to Ayre QB9 (regular USB)
Ayre QB9 to Audio Research LS-25 mk2 (Cardas Golden Ref XLR)
Audio Research LS-25 mk2 to Audio Research DS450m (Cardas Clear Light XLR)
ARC DS450m to Gallo Ref 3.1 or Harbeth SHL5 (Morrow Audio SP4)

The sound is little bright.
What can I do to tame the brightness.
Thanks.

Jay