I agree with Zd 100%.
Your speakers provide three different sets of adjustments for fine tuning their high frequency response. Have you tried all possible combinations of settings?
I would expect that those adjustment provisions would have much greater impact on high frequency rolloff and perceived speed than a change between any reasonably designed cables would provide. If they don't solve the problem, or at least come close to solving it, something other than cables needs to be addressed.
Regards,
-- Al