"VERY trained ears when it comes to sonic difference."
The number of times that gets bandied around in the audiophile world is uncountable to the point it has lost meaning. Many audiophiles think they have superior listening ability. Audio reviewers especially think this. They don’t. They have better than the guy off the street, but in most cases not nearly as good as they think. You also can't hear something that is not there, though you may convince yourself that you do.
If a speaker sounds "dark" it has either an on-axis frequency drop (this one does not appear to), or it has low total energy due to off axis response (this one may depending on the model). As well, this one had treble controls in all likelihood.
A silver cable, plated or otherwise is not going to make any difference to the frequency response of the system, no matter what you or any audiophile may believe. The OP is already using Kimber 8TC cables, which are low inductance, and inductance is a far more important factor in high frequency response than conductor material, insulating material, or any other inconsequential property an audiophile or vendor may invent. Taking some random silver plated or silver cable if anything is going to make the problem worse, not better compared to the 8TC, and is only going to waste the OP’s time and money.