Video : 
Hewlett Packard makes fantastic servers. In my view, there is IBM, HP and DELL that are worth looking at when you talk profisionelle servers.
I've got my hands on an HP DL380 G6. And in this video, we just have a thorough look into that server.
It came as a surprise to me, that it can run with Xeon 55xx and the 56xx series. And handle up to 384 GB memory (Though the ram is so expensive that it is far more profitable to buy a newer server)