I'm probably considered an idiot here, but I bought 12awg OFC copper wire with silver tinning from Amazon
($29 for $25 feet, bought 200 feet), braided it myself, covered with nylon sleeve, and then put on WBT silver banana plugs WBT-USA (wbtusa.com) because I love their screw-down tight connection.
Afternoon of work, sound amazing.
I think, all in, it was $400 to bi-wire, bi-amp, most of the cost being the WBT plugs (which are costly, as such things go).
Considering buying pure 11 gauge silver wire and figuring out how to insulate.