I'm running a similar setup with similar cable, except with 2 less cables: basically two 24' runs of 12 gauge AntiCables under the floor. Speakers have only one set of binding posts, so this is just a true "double-run" of cable. I went to the effort of trying this 4 different ways: cables run simply side-by-side in a "shotgun" type configuration (both conductors of one cable to the "+" terminals and both conductors of the other to the "-" terminals), cables run side-by-side in a typical bi-wire configuration ("+" conductor of both cables to the "+" terminal and "-" conductor of both cables connected to the "-" terminals), and then both of those configurations with the cables twisted together (one full twist about every 6"). Very obvious difference for the better (in this setup, and to my ears) with the bi-wire configuration -- the "shotgun" setup seemed to be a touch smoother on the top end, but robbed initial attack on transients and curtailed overall dynamics to a very noticeable degree. The presentation got boring, if you will. I did not notice much difference with either configuration in the twisted versus untwisted configuration. As the twisted setup was my last trial, I just left them twisted and did not go back and untwist them for a final verification. Happy enough with the result in that config. And the addition of the second set of cables was a very nice improvement overall -- more dynamics, more (apparent) extension in the bass, and more depth to the soundstage.
Your opinions on how to string 25 ft speaker cables
I am running them through a hole in floor to crawl space, then up through floor to speakers. There are four cables to each speaker (Bi-wired)B&W 604s2 plus a subwoofer, Vandersteen 2WQ, (2 cables) nearby. Using 12 AWG two strand 99.9 copper nothing special cable from Monoprice. Should they be twisted around each other, or run separately and far apart, or in some other magical configuration for best of the best of the best, sound?