Apple has today quietly added the ability to configure Mac Pro and Xserve systems with a 3.33GHz Quad-Core processor for an additional $1200 as well as the ability to configure both the quad-core and 8-core models with 2TB hard drives.
The new option of 2TB hard drives priced at $550 each will allow Mac Pro's to contain up to 8TB of internal hard drive space. The same option is available for the Xserve allowing for a total hard drive capacity of 6TB.
[Update - the new options only appear to be available on the U.S. online Apple Store.]