While Image Processor allows you to enter both Width and Height values, it won't distort your images, in your case it would resize them so that they would fit inside of a 400x250 pixel "box". If you want your images to distort so that they are 400x250 no matter what the their initial size was then you'll have make an action and add an Image->Image Size step before your sharpening step.
Thank you for pointing out I was in the wrong forum! Moving on.
"Resize to fit" in Image processor works using the LARGEST measurement. So if you enter 400 x 400 it will resize each image longest edge 400 pixels, accommodating both landcape and portrait. There is a command "fit image" which does the same thing.
If you need to rescale and crop the documents to fit EXACTLY the right dimensions both x and y - then an Action will have to be built. You will need an action for the sharpening anyway.