I think the CD stuff would help or be a good supplement to one's studies, as maximum exposure to the target language is key for really internalizing it. The problem is a lot of those CDs are dull as dirt. Which is why I say listen to something that interests you. If you happen to enjoy anime or Japanese film, knock yourself out watching some every day. You'd be surprised what you pick up from those kind of shows, especially TV series' which have catch phrases or characters who always say the same kind of lines. Plus you'd get used to hearing more informal Japanese which they don't teach you in any course that I know.
