I expect to build a workstation machine based on xeon chip, essentially for having multiple cores and ecc memory. I found on ebay some used xeon E5 chips with low prices, but they are tagged "ES" (engineering samples), or "QS". I searched a bit about these chips, it's said it's illegal to own these chips. They also said that ES chips are not 100% stable, and that's specifically what I'm searching for. ("I don't care" about consumption). They also talk about stepping.
What can you advice ? E3 / E5 / E7 chip ? V1/V2/V3/V4 ? Edit : I prefer E5, in order to add a second processor in future. Used/not used/ES used ?