I have an EVGA Classified x58 motherboard that is revision 1.0. What is the best cpu I can put in it without a hard mod? I was hoping that a xeon x5675 would work right away with a bios update. I was also considering a xeon w3680 if that could work right away. What would be the easiest to overclock as well? I hear the w3680 is fully unlocked but the x5675 has a high enough multiplier. Thanks in advance.  

The two highest model chips for that socket are the Intel i7 990X, or an Xeon X5690 I believe.