First of all maybe you should give a background of what you want to do, because really you are looking at processors for two different needs, ones is a moderate consumer processor (e6500) it would be fine for a standard home user and even a little gaming if you want to make the argument that you don't have much need for more than 2 cores yet. Currently it would be tough to make the argument that there is not enough need yet for additional cores, modern os's and software make it a no brainer to go with quad or more even if you do sacrifice a little clock speed. Also the e6500 has only 2MB cache and 1066 mhz fsb, both of which are ho hum average.
The Xeon you are looking at is designed to be a server/workstation processor, it is quad core and runs 8 threads with hyperthreading. So for the minor loss of total clock speed you more than make up for it with multithreading. The 8MB cache also makes the processor perform much more smoothly and efficiently for buffering instructions. That said, this processor is designed for heavier load/very stable parralel computing, not quick responsive gaming if that is your purpose. Also this processor has an equally unimpressive FSB and ram support, which is a major concern if you need to push your processors usable life further into the future.
Bottom line in my opinion, the e6500 is not a viable option nowadays, 2 cores with no hyperthreading? You may as well be running a 2002 OS with that and suffering the equally bad utilization of your second core. The Xeon is a more viable modern option, but it is not a home user option, the motherboards that accompany it will likely require buffered memory that would cause slightly more latency and would definetely not be preferred gaming option.
