For my subwoofer, I couldn't tell ANY difference no matter how carefully I listened and tried. I swapped interconnects and speaker wire, I even used 24 gauge uninsulated speaker wire and it sounded the same.
My conclusion was that low end frequencies arn't as sensitive to cable as high frequencies in which I definitly noticed a difference.
Since you're bi-amping may I suggest doing it vertically, or using one amp for the highs and lows of one speaker. This helps imaging and dynamics, the effect is similar to using monoblocks verses stereo amps.
Some ppl like using transistor for bass and tube for highs. This still may not sound right lacking consistant dynamics.
If you are using a crossover with only 1db level adjustments, then u may think twice about biamping. Some believe that a 1db difference is actually audible and it will be hard to get the crossover set right.
To set up your crossover do NOT use bass tests to adjust the balance. A starting point could be male vocalists but mostly female vocals. Adjust by ear to get the sound to be neither "head" sound or a "chest" sound. Use a variety of vocals until u don't have to change the levels with different recordings.
If you would like to adjust your bass crossover level more, the sound of wooden drumsticks on cymbals is a great finisher. Just remember that adjusting bass levels can affect the timbre of each instrument.
I just went to a sonic culture weekend event, learned a tip or two from the president of Avantgarde Loudspeakers.