Multiple Merging NADAC integration & volume control

I'm would like use two Merging NADAC (8ch each) in a 9.1.4 home theater system. Unfortunately there is no dealer nearby so I hope you guys can help me figured out some details before to commit the purchase: - Can I configure two devices(8 channels each) to work as a "single" 16 channels unit instead of two separate devices with 8 channels each? - Can I control the volume using the computer volume control (i.e. the volume keyboard keys of my Mac) ? Best, Mihai.