What cables can lower my forward treble.

I have all Synergystic Research Foundation XL interconnects and speaker wire. I have xlr between the cary slp 05  and Pilinus 301 amp. I do have an rca interconnect between Higel Viking cd and the cary.

I second  the Straightwire, I use the Crescendo 2 and 3 if I want a transparent natural neutral cable without losing information. I replaced more expensive cable with the Straightwire and preferred the Crescendo. 

I was of the impression that interconnects with higher capacitance roll off high frequencies.  I don't think it applies to speaker cables though.  You should research this more - maybe it will be of help.  

@12many 

"I was of the impression that interconnects with higher capacitance roll off high frequencies."

With moving magnet phono cartridges where the capacitance acts as a high pass filter and accentuates the treble. It's best to keep the total capacitance between the phono cartridge along with the preamp's input under 220pf in most cases.

There are no cables in existence that can do what you're asking. Physics and the. science of sound prevent something like that from being plausible. If you don't like the sound of your speakers, you need to work on room acoustics, placement, EQ, or just buy different speakers. No amount of money spent on snake oil cables will work.