Lamar Odom would be a better fit. Consider how Odom dominated Marion during their playoff series.
Don't forget how bad Phoenix's defense was. Especially their interior defense. Phoenix shoots a lot of 3's and Marion did get long rebounds off the misses, which padded his stats a little.
If Chicago really wants to make this kind of upgrade, talk to Los Angeles first and see if you can strike a deal for Odom. If that can't be done, look elsewhere.