In reply to:

If your Sony receiver is design to run specifically at 4ohm (which is doubtful)

It is only supposed to be set at 4 ohm when one or more speaker is 6 ohm or less. Since I have 5 speakers that are 6 or less, I've been using the 4 ohm setting. But, I now have it set for 8 ohm for the first time ever and am testing it now. So far things sound very good, but then they did 80% of the time at the 4 ohm setting. More later after I've tried a lot of tests . . .

- Bill

My Home Theater