In reply to Cisco asa 5510.

It depends on what you want to achieve. The DigID audit states that you need to have an IDS/IPS inplace. So a 5510 is not suitable for this. Maybe you have a separate IDS/IPS solution. If not I should recommend a ASA with FirePower. Which model you need depends on the troughput you need. Here you can compare the models and the actual troughput: http://www.cisco.com/c/en/us/products/security/asa-5500-series-next-generation-firewalls/models-comparison.html