Hello,
For Epygi support you would better look in epygi forum(http://support.epygi.com/forum/), but basically you should:
1. create a routing rule on 3cx to route calls to the Epygi_IP:SIP-port,
2. create a call routing rule on Epygi QuadroISDN to route calls to 3cx_IP:SIP_port.
Regards.