" Also, I use Canon's DPP, which doesn't run on Linux."
For Linux :-
PS Elements runs under WIne perfectly - at least the copy I had a few years ago. Otherwise dcraw, ShowPhoto, ufraw and a number of others import Canon RAW files. and allow levels, curves and size/unsharp etc. I've taken to using a script to convert entire collections at one go to have browse-able .jpgs. in the same directories as RAW files. (I've just converted 33GB) In particular dcraw will output 48-bit and showphoto will handle 48 bit
It just requires dcraw and ImageMagick. Just run the script in the directory. dcraw outputs .ppm files
dcraw -w -H 2 *.CR*
mogrify -resize 1624x1080 -quality 100 *.ppm
mogrify -unsharp 0x1+0.5+0.02 *.ppm
mogrify -format jpg *.ppm