Best wire to replace stock wiring in preamp?

Hello,
I own a Parasound P/LD-2000 preamp that I want to modify with better internal wiring.
The stock internal wiring is silver-plated copper. I believe this contributes to this preamps slight brightness and harshness.
I want to buy some aftermarket wiring and rewire the main wires inside the unit.
I still want to retain the tremendous detail, openness, resolution, and sense of space this preamp provides, but at the same time I want to reduce some of the annoying harshness that silver-plated copper is known for.
Do you all think that I should use all copper wiring, or use all silver wiring for the best results?
What brand or brands would you recommend for the very best results?
Any idea on the pricing?
Thanks for your help.