The Quebec club have severed ties with defenders Philippe Billy and Cameron Knowles, midfielders David Testo and Luke Kreamalmeyer and forwards Pierre-Rudolph Mayard and Marco Terminesi.
The sextet join Ali Gerba - currently sidelined with a knee injury - as current Impact players who will not be with the club next year.
Head coach Marsch said the evaluation camp held last week gave him some good insight to who he needs and who of those on the NASL list will not be required for the club's debut top flight season.
"I wanted to see the players a little bit closer, in action on the field, but also to better evaluate who they are," Marsch said in a statement released by the club.
"If a player wants to be successful individually, he must also understand the reality of collective play while helping others to reach their potential. I did not have a lot of surprises during the camp.
"However, I saw little details that I had not seen before."