There are 2 different versions of SEP ver 11.0 & ver 12.0. RU5 is for version 11.0 and the SPC you mentioned is for SEP 12.0 also commonly known as Small Business.
SEPM(Symantec Endpoint Protection Manager) & SPC(Symantec Protection Centre) are 2 different management consoles and they are not compatible with each other.(SPC & SEP 11 clients and SEPM and sep 12 clients are not compatible)
For SEP ver 12.0
Symantec Endpoint Protection Small Business Edition adds operating system support on the client for the following platforms:
Microsoft Windows 7 (All versions)
Microsoft Windows 2008 R2
Microsoft Windows 2008 SP2
Microsoft Windows Vista SP2
Symantec Endpoint Protection Small Business Edition adds operating system support on the server (Symantec Protection Center) for the following platforms:
Microsoft Windows 2008 R2
Microsoft Windows 2008 SP2
For SEP ver 11.0 the latest version is RU6
Release Update 6 (RU6)
What's new in this version
The current release includes the following improvements that make Symantec Endpoint Protection and Symantec Network Access Control easier and more efficient to use.
Symantec Endpoint Protection Manager now supports the following operating systems:
Microsoft Windows Server 2008 Service Pack 2 (all editions except for Itanium)
Microsoft Windows Server 2008 R2 (all editions except for Itanium)
Symantec Endpoint Protection includes client software to run on a Macintosh computer. The client runs on the following versions of Mac OS X:
Mac OS 10.4
Mac OS 10.5
"Also if am to do migration on both the server and work station" The answer is YES you need to upgrade both