What are a few good mid priced Diesel Engines?
Some possible suggestions:
GE DASH 8-40CW
(https://shop.bachmanntrains.com/images/N_Scale/67352.jpg)
EMD SD9
(https://shop.bachmanntrains.com/images/N_Scale/62351.jpg)
EMD SD45
(https://shop.bachmanntrains.com/images/N_Scale/66451.jpg)
ALCO RS-3
(https://shop.bachmanntrains.com/images/N_Scale/64255.jpg)
or the DD40AX
(http://mrr.trains.com/-/media/import/images/1/7/6/1e2.jpg?mw=600)