Can any Audioquest Midnight be biwired?

Yes, you can. Current I'm using internal biwiring (single wire) but you can also use double biwire which has better bass and resolution.

I had the Midnight+, biwired. They were factory terminated for the crossover frequency in my speakers. They were seperated differently. Depending on your speakers, they terminated with more wires going to the lows or highs. I emailed Audioquest at the time and they responded, explaining how and why it is done.

Yes you can buy them with internal bi-wire. Cable has 14 conductors and bi-wire cable and single wire cable are the same, just split up different at the speaker end.

It may be cheaper to buy used 2nd set used here for double run as opposed to sending back to factory for internal bi-wire re-termination. There was a post here recently about the outrageous charges some companies charge for custom cable work. Even if they are close to the same price get double runs, gives superior sound quality.

These cables can be sent back to AudioQuest for re-termination. I contacted them last year and the price was reasonable. Send them an email. This cable has been discontinued, so if you keep your eyes open you might find a good deal.