OpenVPN Performance, specifically number of connections

[limecat]

I am trying to figure out how one determines max number of active OpenVPN tunnels a server can handle.  Specifically, is it a function more of RAM?  Is there any reason a pfsense box like this:
http://www.hacom.net/catalog/jupiter-iii-1u-server-pfsense-appliance
couldnt handle several thousand OpenVPN tunnels (as it can handle several thousand IPsec)?

Any pointers would be appreciated.