The old Polks are a different type of speaker. They do fill the room with sound. But i see no reason the M80's should not do the same. The cab dimentions are different, as the Polks are a tad higher at 44" and wider. But the M80's are a lot deeper at 17".
I'm not sure that the total cab volume is not close on both.
The port thing i have no clue about. The placement....I'm not sure about. I see no reason why i should not fire these strait ahead, like the polks. To fill the room with sound. The placement on the back wall may be an issue...that makes more sence to me. But again, all i can do is try them out in my stock position..then work from there.
