Hi Anas,
You can go with CUCM 10.X on UCS Platform which can support up to 10,000 endpoint.
Refer below links for more insight OVA and Hardware requirement.
docwiki.cisco.com/wiki/Virtualization_for_Cisco_Unified_Communications_Manager_(CUCM)#Version_10.x
http://docwiki.cisco.com/wiki/UC_Virtualization_Supported_Hardware#UC_on_UCS_Tested_Reference_Configurations
Regards,
Mohammed Noorulla Khan