Let me be blasphemous and suggest you do not search for speaker cables that "match the speed" of Valhalla IC's but instead take advantage of that speed. I use Vallhalla's as IC's throughout, including as digital cable. I am using PAD Venusta biwire speaker cables which I find to be a perfect balance to the Valhallas. If you get speaker cables to "match their speed" my bet is you will find the sound too "hot". With the Venustas, you will get a fuller, more natural sound. I had Ensemble Megaflux speaker cables which were as fast and detailed as Valhallas but led to a tipped up, almost etched sound. AZ Satori shotguns also work well, but the Venustas are better. Just another view.
Neal
Neal