Quick update:

Screen works great, and the smell is totally acceptable.

The Diamond USB 7.1 out dongle is functional, but not satisfactory.

In particular, the manual discloses that the optical-out is not supported under Mac OS X, which means that I have run 1/4 inch-to-RCA connections to the multi-channel in on the receiver. Unfortunately, the receiver only has six analog ins for that style of input and the result is that in a 6.1 config, the center rear channel is silent. Additionally, as the receiver is both basic and pretty old for an A/V unit, activating the multi channel-in disables the onboard surround circuitry, turning the unit into a pass-through device.

Therefore, if the audio from the Mac is not high-definition, I can’t have the receiver doctor it up. So that’s no good.

Additionally, two of the channels seem to have a bit of crackle in them when driven by the analog input. It could be the speakers, or the cables, or the speaker wire, or the 1/4 inch jacks. So with the analog multichannel in, the number of possible points of failure becomes prohibitive to isolate.

What else?

Oh yeah, the projector seems to perform best if inverted, but I don’t have a true VESA-style ceiling mount, so the device is resting on its back on an articulating keyboard shelf I dumpstered years ago.

Cables dressed, speakers hung. Nearly there.