My expectations this window were about 4 incomings to spice things up a bit; so a good start to that!
If we stay 3-5-2 its a midfielder and a right wing back, although that would be strange considering the comments regarding Miller and his reasons for wanting away from Rotherham.
If we were to switch to 4-3-3 I would probably opt for an experienced midfielder who can keep possession and a Goal keeper.
4-3-3 I think would be a clever move as it would actually utilize Marshall, Adams , Korboa and Chuck better.