Mark Levinson 27 Clipping

Yes, it's likely to be, or do, damage. Yours and any other amp. "Regualr" clipping is not a good thing, as Sean said. You, more likely, will do damage to your speakers, first. More power, more efficient speakers, or lower volumes. That'll solve your problem. Good luck out there.

Do NOT play loud. At best, you'll blow the fuses on the ML. HOWEVER, if you hit upon a very fast transient, more damage can occur -- as stated above -- to the ribbons on the Duetta (not easy to fix nowadays)... the fuse might not cut the signal off in time!
The Duettas are not as bad a load as other Apogees (i.e. they're less "bumpy") -- but I still used to send a Krell 80 into shut-down on orchestral pieces and no, the volume was not all the way up-- far from it :)! Happy holidays!

I don't know what the specs of the Apogee's are, but I ran my ML 27 with Thiel 3.6's, which are 4 ohm speakers rated at 86db and never had a problem. It played them loud and clean.

Thanks for responding (this site is #$@*&+ great). A rep from Audio Consultants in Evanston IL emailed me w/ the following,"The 27 has a soft clipping circuit and other protection circuitry, so there is no danger here". I suppose the speakers might be on thinner ice than the amp during a clipping episode. My experience w/ Scintillas and Duettas (tho' brief) seems to parallel Greg's. I've heard things start to choke even w/ some pretty testicular amps at way lower than a live performance volume.

Duane, the Duettas are a MUCH kinder load than the Scintilla... Duetta is a load; Scintilla is a short-circuit :).
Merry Xmas everyone!