Update to my post #11 above.

I have to eat crow on my earlier accusation that the Bose (Clarion) headunit was responsible for the cutting-out of my signals. It turns out that it was my Peripheral Line Out Converter (LOC).

I took my car to my installer just to make sure it wasn't an issue w/ my aftermarket equipment before I went to the Infiniti Dealer. My installer was as puzzled about the source of the cutting in and out of the signal as I was, and he just happened to shake the LOC (is this a standard troubleshooting procedure?) - and then he immediately induced the signal cutting in and out. In any event, we connected the speaker level output directly to the amp, and my car's back to normal. Some would maintain that a LOC is necessary for our Bose systems. I won't argue, but for my purposes, my amp does a decent enough job, and my Boston's are sounding good again.