Hello
Just my advice..
Stick with your original goals, which to get small system with good sound.
First of, the basic system you can get will be just stereo (and maybe plus a subwoofer). In this case, i really recommend you to look at NAD L53 / L54, or NAD L73 for all in one 5 channels system.
You have to know the wattage of the receiver you are going to have. This will determine what kind of speaker you should get. Look at the speaker spec (example: Min 15 watts, max 150 watts). NAD at 50 watts will drive those speakers just fine. However, with other brands (specially those japanese brands like Sony, Pioneer, etc), you might need to use receiver at at least 80 or 100 watts.
If your receiver have only 50 watts, don't even try to use B&W speakers who have min 50 watts requirement. (It will work, but it won't sound very good). In fact, go as far as you can from minimum spec (but lower than max).
Low wattage spec speakers such as PSB B25, Paragidm Monitor, or Studio are my best advice.
ANd oh, please disregard efficiency and/or loudness of your speakers. It won't matter at all. If you live in small apartment, chances are, you are never going to have them really loud anyway. Sound quality should be your #1 priority.
Second, it's the speaker size. I never believe in small speakers. I don't care what they say in advertisement, small speakers will make small sound. Do not get speaker smaller than 5.25" diameter.
Happy listening !