Does anyone have an opinion as to whether it is best to stick with one brand of cable for bi-wiring?
If your goal is making your speaker sound more coherent, then sticking to one brand of wire is a good idea. I would even recommend making sure that the two cables of a biwire set are very close in design or identical if possible. The importance of this will have a lot to do with the speaker you have.
If the speaker is a two-way design, where the crossover point occurs in the critical midrange, it becomes more important that the two cables are identical or very nearly the same. In a three-way, where the crossover point occurs at a much lower frequency, you can often get away with a less expensive cable for the bass. Be aware that three-way speakers with more gradual crossover slopes (1st order) or a somewhat higher crossover point between the midrange and woofer, will benefit more from a nearly identical or better quality cable to the bass. Or to put it another way, they will show the limitations of an inferior or vastly different cable design used in the bottom half of the biwire.
