No, Chris; the people who ran a lab test on the 606(see the excellent
HomeTheater Magazine lab test and review)don't "know" of this 4 ohm problem either. Note the substantial power measured into 4 ohms at the more realistic 2-channels driven standard measurement. Many owners report using similar receivers with satisfaction on speakers more difficult to drive than the M80s.
In my view it's an excess of caution to allow the choice of receiver to veto the choice of speaker. A problem shouldn't be assumed that may never develop if the equipment is used sensibly.
