Just switched from Sophos to SBE 12.1.3

I have a client that I just switched yesterday to 12.1.3 from Sophos 10.0.  The enviroment has a Windows 2008 Stanard server with 8gb running Sage Mas90 4.3. Some PCs are XP and some are Windows 7.  I excluded the drive mapping that has the drive mapping to the shared directory and the Mas90 executable. I am looking for advise on what I can do to speed this up.

Previously there was no antivirus client or virus managment on the server.  Now there is.  Should I remove the antivirus client from the server?

In Sophos I only had the on demand scanning set to read and another else.  Should I change to just doing that?

Any sugesstions would be appreciated.