dual Xeons OEM ??

[NaeKuh]

iirc the only difference between OEM and retail is that one comes with a cooler and the other does not

NO.

Retail = full warrenty Via Intel direct and typically in excess of 3 yrs.

OEM = Vendor Limited Warrenty.
Meaning ur at the mercy of the vendor.

If your getting it via Ebay, you probably only have DOA on it.
Meaning they will just gaurentee that its not Dead on Arival.
But once that cpu dies, you will be out of luck.

ok cool, and what about the warranty?
I mean if i OC my cpus, does it avoid the warranty?

Yes.

However chances given you will probably lie to intel anyhow.
But to answer your warrenty question, if your so firm on warrenty, get the retail package.
on OEM typically it doesnt last longer then 30 days.... unless its newegg, which they do offer 1 yr OEM warranties.