If I were you I'd pass on the subwoofer and the surround and get a pair of really nice bookshelves. Since most Netflix movies aren't even streamed in surround, and virtually all music is recorded in stereo, your benefit from the 3 extra speakers will be minimal. The subwoofer in an apartment could also be a neighbor problem so I wouldn't even bother with it.
For $400 bucks you could get a nice pair of speakers for music that won't rattle the house. Also, if you have pre-outs on your receiver, you can get powered studio monitors instead of speakers, just for another option.
I'm actually in a similar situation to you which is why I'm replying. Only difference is I already have a 5.1 setup with decent bookshelves, and I'm thinking about downsizing to a higher-quality pair of stereo speakers and calling it a day.