you can, I see it done many times
put one in a x58 system and let it rip
I seen a 2.4ghz xeon clock to 4ghz
with the right setup they're the best cpu for ocing
let me just find a few links
edit
here is someone with a 6 core one, overclocking
http://www.overclockers.com/forums/showthread.php?t=714828&highlight=xeon
xeons are higher binned cpu's witch make the run far cooler and far more stable, witch = more ocing
the only hard part about ocing a xeon is finding the right mobo, don't look for a sever mobo, many top of the line desktop ones support xeons
OP
what cpu and motherboard do you have ?