Hello,
According to Cisco Performance docummentation you will be more than fine.
Now regarding IPv6 being supported. For cisco Dedicated firewall appliances the support for IPv6 started on version 7.0.1.
Due to memory requirements I do not think ur firewall support that version hence IPv6 will not be supported.
Regards,
Jcarvaja
Julio Carvajal
Senior Network Security and Core Specialist
CCIE #42930, 2xCCNP, JNCIP-SEC