I don't know your system, but just my experience. My system is budget high end. I really was impressed with the Heimdall IC's (have two pair now). I thought they were fast, clean, and on the slightly warm and sweet side sonically. Complimentary to my system. I thought the same as you and splurged for the Heimdall speaker cables. I ran them for several weeks, but my system was consistently much less listenable. Probably exposed my budget components too much, but I had to pull them out. Worked a downgrade to the Blue Heavens and was much happier with the result.
I had this same result with another popular high resolution speaker cable so its not unique to Nordost. My point is to audition or have a money back guarantee if it doesn't work in your system.