I am about to pull the trigger on a pair of Axiom M60's. With the way my room is setup, I'd have to put the right tower about a foot and a half in front of the end of a long couch. The part of the couch that would be blocking the bottom of the tower is about a little less than knee high. I figure that would cover the bottom 6.5 woofer from view in my listening area, and maybe a portion of the next 6.5 woofer in the array of 4 speakers. Granted they are ported woofers and there is a foot and a half distance between the couch and the tower, will this noticeably change the sound quality at my listening area?

A couch in front of your speaker will most certainly affect your audio in a negative manner.