Hi i just curious that can I use the bi-wire cable to connect to my receiver in bi-amp mode (biwire to biwire at both ends)? Why there is no such cable in the market as I tried to find it? Or separated cable would be a better idea?
You can use four core wire. All you have to do is keep the corresponding colours to the correct binding posts on the AV amp and the speakers. Make sure you give enough of the single wires to be able to connect easily.
If you are correctly bi-amping, ie, two separate identical amps then it would be better to use traditional two core. If you are bi-amping from a single AV amp then I don't really think that brings any real gains. You will still be drawing power from the same PSU and thus reducing the power available to the remaining connected speakers.