I didn't build this rig, but was called to help troubleshoot an audio issue. He was getting these ticks, pops & clicks that would come and go randomly, over any audio he played back, using multiple players. Recorded material was not affected. The anomalies only occurred during playback and only on his machine(same content played fine on other PCs.) It happened with local content and even streaming a 1K test tone over the net. He was using the Asus Rampage IV which has a Wireless Wifi chip on the motherboard; it was causing all of this. The WiFi worked fine. Disabling this adapter was the "fix" until he could run a CAT5 cable to the next room. You would be surprised at what sensitive audio equipment can pick up.
I don't have a specific motherboard recommendation so much as advice on what to beware of in setting up a rig like this. Any Socket 2011 motherboard will probably do just fine for your client.