Bearing in mind cables should be thought of as the synergistic link between any two components, and I may have used differing equipment than you...
I used to have 750 shotgun speaker cables that worked wonderfully with some Coincident Technology Total Eclipse, Egglestonworks Fontaine, and assorted Tyler Acoustic and B&W loudspeakers. However, they did not respond well to Vandersteen IIIa sigs and my current VR4 SE's. Exhibiting allmost the exact opposite qualities that MIT usually delivers. The midrange hardened up, soundstage depth was forshortened, along with a distinct lake of air up top. Decidedly NOT the usual MIT traits. I still use Oracle V3.1 between my Sony XA9000ES and BAT pre, and 330 Shotgun from pre to Spectron amp. I now use Acoustic Zen Satori Shotgun for the 4 SE's with a midband to die for! Another great bang for the buck cable product line is the Luminous Audio stuff. I use their Silver Reference, along with the Zen Silver REF for my multichannel IC's.
Again, just because a particular cable does not sound good with a particular speaker, does not make either product less worthy. They just don't "like" each other. This is why cable reviews are frought with difficulty. They must be tried out with a wide array of products.