Hello again,
For what we would be sending, it really depends on your settings. If you are quarantining spam, doing a lot of reporting, and so on we really don't like to suggest that you have a scanner remote to the Control Center. We see more issues with that than what good there is from doing it.
Not to say it isn't possible, but you would need to trim what the appliance is doing and keep an eye on usage.
For the appliance, the software is fairly similar to what you are already used to with SMTP 5. So if you are setup how you want it to work now, the appliance should be able to do the same. As well as have more functionality. There are multiple Hardware choices for the Appliance including a Virtualized version that currently runs on ESX.
Being in support though, you would probably be better served to talk to a sales engineer for specifics on offerings. I believe you should even be able to do a "try and buy" for the appliance to see how you like it.
Thanks!