AMD QUESTION: Clawhammer vs. Sledgehammer

[HAVOC]

Hey, can anyone help me here. A friend of mine and I are going to build a gaming PC to use as a DEMO GAMING RIG in his shop. We are going to use a AMD Athlon 64 4000+.

We've found 2 cores available:

Clawhammer OEM = $575.00
Sledgehammer RETAIL = $544.99

Both specs are exactly the same, just a different core:
Is one better than the other? If so why? What's the deal?

Please explain... Thanks a lot...

EDIT: UM... I think this must be a newegg.com typo! Check it out.
http://www.newegg.com/app/ViewProductDesc.asp?description=19-103-497&depa=1