Can you convert the CAD file to EPS?
Unless you want to edit the CAD file after you've edited the image in Photoshop there's no need for a program that displays both raster and vector. You won't be able to resize the CAD part as you would with a vector file because you would then lose the alignment of the raster image.
If you really need a program to display both, then Illustrator is the answer: it can import both the Photoshop and the CAD files.
