Ya. I see that but Intel is saying these are more powerful.
The Intel Xeon processor E5-4600 product family delivers up to 88 percent higher performance1 than a comparable Intel Xeon processor E5-2600 product family-based server and up to 3.8x2 the prior generation 2-socket Intel® Xeon® processor 5600 series-based server.
They're also quad-core and have dual sockets.
whats the difference ? Other than these seem more powerful and come in quad core dual sockets.
E3 are for workstations and servers, but they cap out in performance where E5-1600 begins and have less expandability and IO bandwidth. One advantage right now would be that they are moving to Ivy Bridge, but that isn't some magic jump in performance. One CPU per system.
E5-1600 are for workstations. You could use them in servers too but they have high heat output and you can get dual processor systems for similar prices which would usually be better suited to server usage and support more memory.
E5-2400 are for cheaper servers, losing out on some of the I/O and memory bandwidth/capacity of the 2600s to reduce costs.
E5-2600 are for servers and workstations, these will make up the bulk of the Xeon sales and you will see them in servers of all sizes from blades to 6U.
E5-4600 is based off the same LGA 2011 socket as the 1600 and 2600 and and just allows 4 processors.
E7 until now has been the only way to get more than 2 Intel CPUs in a system, it also offers some other features over E5-4600 for the type of customers who want to deploy multi-processor systems. It's future remains to be seen as there, at my last look, will not be a Sandy Bridge-EX. It will be skipped and Ivy-Bridge-EX will be the next iteration, maybe because they can easily deploy 10-core (already available with Westmere-EX) without major cost additions.
Apple will surely use E5-1600 and 2600. Not only because they directly replace what Apple have been using, but because it will be cheaper to deploy and offers expandability. Using E3 means a different board type and limited features over what is already on the Mac Pro.