Why is he pissed? I assume he has custom sound hardware anyway, what can't he do with the last gen Xeon he can with the latest gen Xeon? It's Xeons...in a box. Most editors (video/sound) would be provided with fibre storage links from an all-in-one vendor, whilst it might be nice to see thunderbolt on a mac pro, you can't put infiniband on an imac...
Audio folks like to have as much power as possible - it allows them to pile on plugin after plugin without much fuss.
Every bit of CPU power gained from an upgrade is promptly put to use in doing audio processing .. and I would imagine that this Audio guy is probably using Pro Tools or Logic, and has reached the ceiling for what he can do without upgrading to a faster CPU.
Fact is, Mac Pro's are no longer the really best solution for a high-end audio/studio situation - sure, they look good as furniture, but for the same price you can get 2x the number of plugins running on self-built hardware. This matters in the audio business.
(Disclaimer: My DAW is a Linux machine. It rocks. I also have a portable DAW: Macbook Pro. It also rocks.)
