AMD Processors

Is there any reason you HAVE to go AMD do you have an AMD motherboard that you don't want to replace? Personally I would go with Intel's Xeon since they are more efficent and faster than the AMD CPU's.

The Opteron 6200 series is their most powerful, with the 6284 SE model being the top of the mountain.
http://www.amd.com/us/products/server/processors/6000-s...

What is intels most powerful CPU for server use?

If you really have to go AMD I would go with the AM3 based Opteron CPU's, the Bulldozer server CPU's really aren't that impressive.

The Xeon E5-2687W would be one of thie most powerful CPU's.