Hi,
You can install SEP as a standalone make sure you are aware of this.
SEP has three feature i) Antivirus & Antispyware ii) Proactive threat protection(PTP) iii) Network Threat Protection (NTP)
If you are planning to upgrade manually then you will have to use Intelligent updater.
But intelligent updater can only update Antivirus and Antispyware. For PTP & NTP you must have connection either with SEP server or Internet or Live update administrator (LUA)
You can get the Symantec Protection Suite Enterprise Edition Trial Edition here
-https://www4.symantec.com/Vrt/offer?a_id=96485
At this location you will get SEP 12.1.
Are you looking for SEP 11 or SEP 12.1
SEP 12.1 is the latest Antivirus product by Symantec.
Till date SEP releases
http://bit.ly/m0vOJp