Late reply and you're probably well sorted now, but having seen some wonderful and fairly recent (last ten years anyway) Klipsch-Corner Horns wired with a chunky-but-cheap mutli-strand cable (one of the "clear-jacket" types), I'd suggest a good 2.5mm copper cable available on eBay and elsewhere for around £2.50 per metre. That's assuming you don't feel cheated about using something so inexpensive of course...