This question has been moved from 'Best Practices in Security protection' to 'Web Gateway' in Email & Web Security.
There was a similar question asked in late 2010 - see https://community.mcafee.com/message/166409#166409
where the reply stated
the blade is intented to be deployed at huge sites
- which may apply to your DoD customer.
Someone who knows about these things should see this and (hopefully) give you an answer.
please get in touch with a local sales representative. They can explain the best options for this requirement, since they have the experience from similar customers and expertise to make a proper assumption of what is required.