I currently have 4GB of RAM which has been fine for the most part.  Any reason to upgrade to 8GB or more?  I run PMS, SAB, SB, CP and NZBDrone

I have a rule... Max out every motherboard!

...  Any reason to upgrade to 8GB or more?

 

"... or more" is not an option => your board only supports a max of 8GB  (unless SuperMicro's specfiications are wrong ... I HAVE seen cases where their boards will support larger modules than they say).

 

As for upgrading ... if you're happy with the performance with 4GB, I'd just leave it as is.  With unbuffered RAM, your memory subsystem will be more reliable with only 2 modules installed, even though the board will hold 4.    The bus loading with 4 installed modules causes notable signal distortion on the memory bus.    If you need the memory (e.g. for virtualization support) then by all means go ahead and upgrade -- but I'd definitely use all ECC modules in that case.

 

... a better path to go if you decide you want more memory is to just do a system refresh, and move to a Haswell-based system where you can use a pair of 8GB modules to give you 16GB with only two modules.

 

I run many plugins (see my signature). Only because of running a virtual machine did I need to upgrade from 4GB to 8GB of ram.

 

I use the "Stats" tab in the Dynamix WebGUI to see how much ram I'm using and I'm always surprised how little I actually use (<4GB) when not running a virtual machine with 4GB ram.