You haven't detailed your system but i'm guessing yor speaker cable is QED silver. Detailed, open and tranparent the reviews might suggest. In reality with a brightness issue you have a screaming Jonatham Ross on amphetamines
Due to the brightness of CD recording over the last decade or so, your CD player is the most likely hi-fi component to highlight (not cause) a brightness issue in your system.
I could be way off hear but i've experiance this problem myself with QED in the past (Arcam A22 & Mission 774 speakers) - QED sounded awful, changed to van den hal CS 122 sounded great. I am now using Chord Rumour (bi wired) with my system below
Go back to your dealer and ask if you can demo some cables at home. Most will if you ask nicely, offer a refundable deposit, they've got your money if they sort the problem