Hey, thanks for responding Selden.
It's not my problem... as I said, we were toubleshooting someone else's system. The thread is linked
here, if you're interested. Yes, I'm well aware of the impedance setting and the issues surrounding it, however the OP in that thread may not have been (an AVR rookie), so we were attempting to identify possible causes of his problem.
Interestingly, I looked at the X5200's and X4000's manuals side-by-side, and there is in fact
no equivalent instructions in the X4000 manual for changing the impedance setting. It simply says:
Use speakers with an impedance of 6 – 16 Ω/ohms. That's it. So 4Ω speakers aren't
officially sanctioned, the EC's aren't obliged to torture test it into 4Ω loads and therefore a "gelding switch" is not required. Brilliant!