Speccing a Xeon is pretty much throwing money straight down the toilet for CAD, since there's very limited use of all the cores and features in that processor. Running a multi-user database a Xeon is excellent. For CAD/C3D? nope. And the ECC Ram Xeons require is more expensive, and not beneficial in CAD.
See the recent Ars Technica article on Intel processors for a good discussion on the modesl/features and identifiers.
And seriously -- look at Boxx and compare their offerings to Lenovo. At least the folk at Boxx and Xi know how to spell CAD