if you have the money to buy a xeon 5649 i would suggest that you save a little and buy a i7-970 which is also a hex core, but you can clock it much higher. also as its been said it depends on what u are going to use it for, but since you had a xeon before, i guess you do use a lot of cpu intensive programs.
As for suggesting a SB chip... if you're just gaming then the amount you save would be worth it, but then again since you have a 1366 platform i assume you wouldn't want to buy a new mobo/ram etc.
so yea, my 2cents are get a i7-970