Questions for configuration, is this VM for me?

Hi. I am interested in building a system to use Parallels workstation. I want to utilize VT-d for media applications.
I have a few questions on what is and isn't possible.
#1 Can a device be disabled for the host and accessible to the guest only? I would like to do this to insulate the host from the internet over the LAN, without needing a firewall.
#2 Is use of 1394a possible? Also in Linux? There is still DMA for the guest OS?
#3 How many guests can be run at the same time? Do they have customized hardware profiles?
#4 Is there a mechanism for transferring files between guests? Guests and host?

Ideally I would like to set up custom user profiles as guest OSes for different tasks. Also with the ability to insulate DMA access between them.
I heard that Parallels is the best for workstations at this time, and the Graphics Passthrough demo is very impressive!
Thanks.