2 Shielded 18/2 cables for 2 XLR ports should be fine. You may also want to provide the customer with ground loop adapters and depending how you are terminating at the receiver end, if it is not XLR or balanced, RDL makes a lot of great items for that.
-- Thanks, Anil A. Apple Communication LLC. www.apple-link.com Pro-AV - Pro Lighting - Networking - Security Cameras - Home Theater For all your low voltage cabling needs
