100% agreed, stick to an Intel Xeon E3 series (v1, v2, or v3). You should be able to find the V1s for around the same price as those older Dual Xeons, but will be worlds better for Minecraft.
I slightly disagree. For home servers, the most efficient chip makes sense. Its likely to be a small server requiring less performance and the power bill matters. For server hosts like your employer(or maybe you own the company, fuck if I know), the Xeon chips make sense because you have cheap power and your customers could be wanting to host larger servers.