For the Intel vs AMD question you will have different answers depending who answers. Both servers are good options. For the control panel, I would say that Plesk is better bur I do not know a lot about Direct Admin.
Cpanel is the best control panel hands down. Plesk has a nice user interface (it looks alot like windows) but Cpanel has the most features.
You could also try Interworx. Many hosting companies are now preinstalling interworx, but you can always install it on a control panel-less machine.