Hello Matthew,
As you said, System Center Essentials 2010 is designed for mid-sized organizations (up to 500 PCs and 50 servers). For a larger environment, Essentials may be not a proper choice. I would suggest System Center 2012 for your consideration.
With System Center 2012, you get the most cost effective and flexible platform for managing and updating your client computers and devices.
For your reference, more details are provided from the webpage below:
System Center 2012
http://technet.microsoft.com/en-us/systemcenter/hh880681.aspx
Thanks,
Yog Li
TechNet Community Support
