For biwiring, you want the split into the two cables as close to the amplifier as possible. This is so that the maximum length of the path isolates the bass and mid/tweeter signals. So, even if the two pairs of binding posts are very close together, you still want to split the speaker cable close to the amp.
The Masterbuilt cables come in three levels: the Purple Line intro level, the Standard, and the Signature. The list for 8' biwire speaker cables are/were (the last time I asked) $1250, $3500, and $6000 respectively.