I just biwired my DIY speakers, which I built to allow it. I had my old cable hooked up to them for a few months already. I honestly can not tell the difference. I'm using 11ga Canare 4s11 cable in a 'shotgun' config now. Each piece is the thickest cable I've ever used, and I'm using two for each channel.

I heard a much bigger difference when I swapped my tubes in my preamp. There was a noticable change in the soundstage. This cost about the same as the cable (which was inexpensive.)

Some tweaks are worth the effort, others just aren't.