There's a reason people pay much, much more for E5s than E3s, and it's not for clock speed. You can't get more than 32 GB of RAM in an E3 server, for example, w

There's a reason people pay much, much more for E5s than E3s, and it's not for clock speed. You can't get more than 32 GB of RAM in an E3 server, for example, while E5 servers can handle 256 per processor. E5s can coordinate between processors for multi processor machines, too.