I used to have a 3808 and although it ran the M80's quite fine, I believe if you look in the manual for then Denon 3310 or 3311 you will see it specifies no lower than 6 ohm speakers. I think it was page 3. It wasn't until the 4xxx that Denon recommended no lower than a 4 ohm. That is not to say the 33xx will not run a 4 ohm quite sufficiently, but if you are like sirquack was with the Emo a few years back ................. you might just run a little hot.
The 3311 here in Canada I priced this weekend at $1150 I think the 4311 was $500 in the difference.

Anthem MRX520
M5HPv4
VP160HPv4
QS10v4