Biwire B&W 803D with different Cardas Cables ?

I have a pair of B&W 803D, Luxman l-509u integrated amp and Luxman D06 SACD player.

I have Cardas Golden Reference XLR interconnects 1mt and a pair of Cardas Golden Reference monowire 2,5mt speaker cables.

My speakers sound bad with monowire cable and B&W jumpers.

I will try Cardas jumpers (a friend of mine will give me his Cardas jumpers he doesn't use anymore) but i want a real biwire solution.

I think B&W 803D has very different needings for its bass section (3 woofers for each speaker!) and its mid-highs section, so I am thinking of biwiring them with my Golden Reference (5 AWG) for bass, and a pair of less expensive Neutral Reference (8,5 AWG) for mid-highs.

I really think bass section of B&W 803D (speakers are not all the same!) needs a thicker cable than mid-highs.

Now I am using my Golden Reference for bass, and my old Audioquest Gibraltar biwire 3mt for mid highs (using only 2 of the 4 spades on the speaker end)... it sounds better than jumpers, but bass is a bit "swollen" (maybe it's G.R. XLR interconnects? I am sure it is is "warmer" than G.R. speaker cable, more neutral) , and high frequencies "come out" only at higher volumes.

Gibraltar is longer than Golden Reference (3 vs 2,5 mt) and its conductor are not so thick (12AWG) as G.R., so I think it conducts VERY less power to the midrange and nautilus tweeter.

Neutral reference could be a good idea, or should i buy another G.R. ?

I am afraid that bringing the same power to the 3 woofers of each 803D and to the mid-tweeter could shift tonal balance towards mid-high frequencies ...

What do yuou think about that ?

Many thanks

Emanuele from Italy