Here's a train that would go perfect with your E series trains and would also be excellent in Railworks. This was the first streamlined diesel locomotive to be built in the US in 1937 and was the first E-Unit of the series.
It would look great running freight or express with your E7,E8 and the E9.
Here's several vintage photo's of it, there aren't many left, the engine would have been very similar to the later E-Units and the F-Units.
And here's the only real cab photo available for the engine.