I am having a Canon 135 F2.0 L and a 70-200 F4 L IS ( rarely using them ) . I never own a 70-200 F 2.8 IS but I am always thinking about getting this great but heavy (?) lens. Should I sell ( or trade ) the 2 lenses above for the 70-200 F 2.8 IS ( mark I / II ) or should I keep them. ? I am using Canon 5 D II . Any advice, please .