This shouldn't be too hard to implement, I hope...
For each directory displayed in Known Files, show the number of files in the directory, in one's mylist and not in one's mylist, for example:
"Area 88 [A-Kraze] | 2.04 GB | 12 (12/0)"
Combined with a flat directory list (e.g. all directories are listed in the same level of the list) and sorting the flattened list by the number of not-in-mylist-files, this could prove to be a useful feauture for managing newly downloaded files easily.