Bryston 14BST and Polk SDA SRS Speaker Cable?

I'm currently running some thick Monster Cable (model number escapes me) speaker cable and would like to upgrade to a bi wire set up for this rig. I'm pushing a lot of power and like to listen to rock and blues music on the loud side. I'd like a cleaner (less muddy?) midrange (if this is possible with a cable adjustment). Top and bottom end are fine. Current research has me leaning to bi wire Kimber 8 TCs or an Alpha Core M1 bi wire. Used recommended a new "Wireworld Atlantis III+ Internal Biwire" as the "perfect" match. However, I'm a tad skeptical, as this cable is the one currently on a special purchase on their sister company, "The Cable Company". Any suggestions in the $500 range?
used XLO TYPE 5 is a excellent cable at today's prices.
I think you'll like Alpha Core MI 2 if you want to clean up the midrange and still get a bang at both frequency extremes. What Polk's are you using, I used to use the srs sda 2.3tl's, in fact I still have them but not in any system.
I'm using the 1985 version Polk SDA SRS which has 8 mid/low drivers coupled to a 15" passive radiator and four tweeters per cabinet. I picked them up off of E-bay this spring. I was using a Parasound amp pushing around 220 watts a channel. Sound was good but a little lean. I picked up the Bryston 14 around a month ago and it's spec sheet said it tested at 600w at 8 ohms. The Polks are a 5 OHM load. The speakers really opened up with the extra power. I'm also running a Bag End 18" Infrasub which has blended perfectly in the lower end.
Pre amp is a Sony ES9000. It's part of a home theater set up. I started out with some 1984 vintage Polk SDA 2s. Bought them new in 84 and still have them.Thanks for your recommendation.