the Xeon processor was meant to be used for DATA servers where the I7 was meant for graphics, games and personal computing. so the use of the computer is important.
It sounds like you are implying that Xeons can't do desktop tasks well, which couldn't be father from the truth. They often cost more because they can have multi-CPU support and additional caching, but in general they are the same core types as the desktop chips.
To answer the OP's question, a XEON 5160 is really just a Core2Duo E6850 with a little more cache and MP support. Two of them together give you Four 3Ghz Core 2 Duo cores or a Q9650. A Single i7-3770 Ivy bridge should be roughly twice as fast for most CPU limited tasks.