dell typically certfies their servers to run a particular version of redhat. that would probably be a good place to start. you're dealing with a spanking new processor and chipset so there's probably a little excitement to be had in doing that.
In that case it would be RHEL3 which costs money.
1 alternative option could be Whitebox Linux which is RHEL3 built from srpms.
I have it running on a box at home & it seems fine. Updates are a little different but it's all documented on their site.
http://www.whiteboxlinux.org/
-- Mark Farmer Linux System Administrator
