FAST....... Put I can think of a lot better thing that i could be wasting my money on as Xeon have very little use out side being used as SERVERS.
Like one problem that you will have is that you do not have the same things supported on a XEON motherboard as you on others. Eg. Gaming Video Cards.
So if you are thinking about gettng a XEON Set up so you can plug in the biggest ATI or nVidia video card in there so you can play HL2 with every thing maxed out, you are seriously mistaken.