Hi Mark,
I am currently using a tri-cat 5e plenum braid with my st70 and love them, and is dead quiet. My speakers aren't bi ampable or set up for bi-wire.
There are different configurations for the bi-wire. Instead of using one cable as the + and the other -, I would use all the clear of the two cables for one polarity, and the colored wire from the two cables for the opposite polarity. Connected this way the twisted pairs should help nullify any noise, unless the noise is created in your amp.