scorchio,
I have nothing against AMD, but would go with the Xeon config. If you had of asked me a couple of years ago I would have with out hesitation gone for the Opteron processor.
Xeon processor speeds are up there with them now so that's why I would choose it. The rest of the configuration looks really nice, I must say that I'm am some what envious of your customer
HTH,
Cheers.
Ben