Standard scoring or PPR?
What is your line-up requirements? 1 rb, 2 wr, and 1 flex?
McGahee is not an upgrade in your starting lineup over Ingram. Based on your roster, I would stay with your starters.
However, you are carrying too many TEs, so I would drop Miller and pick up McGahee and hope that Moreno gets injured again this year. Even if he doesn't, McGahee could get some points as a TD vulture in spot starts (bye week replacement). That of course is assuming that McGahee is the best rb on the WW.
10 team, PPR, 1 qb 1rb, 2wr, 2flex (rb/wr/te), 1k, 1dst
QB: Stafford, E. Manning
RB: Peterson, Blount, Hightower, Starks, Tate, Tolbert
WR: Nicks, Wayne, Bowe, S. Johnson, M. Thomas