I have not heard of Intel releasing anymore CPUs, not even any K editions. If its and ES, that means it just might have come with a unlocked multiplier but ES versions are normally for mobo makers to test and that means this CPU might have errata that can be very bad.
Honestly, I wouldn't buy it since it will have no warranty and returning to the reseller would probably not happen.
Because this CPU is ES CPU so intel doesnt announce its commercially to the public, nor give this cpu official name. By judging from its clock speed 3.1GHz (2400), unlocked multiplier (K) and HTT (i7), it was named i7-2400k.
As you mentioned, this cpu might has limited functionality and no warranty from maker, so i think i may pass this. Thank you a lot for your advise.
Should wait and see how amd bulldozer will show its cost/performance, and then make decision for my system refresh.