Hi latebloomer,
James should probably clarify that the BDP2 can only output one stream of data at a time. So that means you can use either USB or SPDIF and switch back and forth between them using Manic Moose's interface("Audio Devices" section of the homepage)......but you won't get simultaneous digital output.
As for your Berkely, you will likely have a problem if you are feeding your BDP2 music from an external USB hard drive. Well, I know for a fact that you will have this problem, as I've experienced it first hand. The issue has to do with the how the BDP2's USB ports are configured and the Berkely seems to need an isolated USB port (hopefully Chris can elaborate more on the particulars because its beyond me technically

).
The way around this issue is to use either a network attached storage or to build a SATA drive right into the BDP2. The BDP2's internals are already set up to accept a 2.5" SATA drive and it's pretty straight forward to install/initialize.
Cheers!