I googled xenon 5160 and the first hit was http://ark.intel.com/Product.aspx?id=27219
As to the upgrade I'm going with no. The 3.0 GHz was nearly the top of the line for that model. You may want to ask HP if they had other options like a second CPU.
I have a hp xw8400 server that has the xenon 5160 3.0 ghz processor. Unfortunately I am not knowledgeable about cpus. I know this is an lga 771 type processor.
Can someone tell me if there is an upgrade path to put a more powerful processor in this machine?