So to bi-wire, the speakers must support this. I'm guessing bi-wiring is a 2-wire output to a 4-wire input.

Distance from amp to speakers would be about 30'. It's a new construction, and I haven't yet decided if the components will go in the basement or in the same room as the HT.

Now, what happens if I twist the wires (matching polarity) at both ends, in effect making the 4 wire cable into a 2 wire cable? Would this harm the system? Would this equal a 12ga cable?