As DAVIDF said, we need more info. The dimension of the room are a good place to start.
Depending on the size of the apartment or at least the size of the room the Audio system will be in, will determine how far you want to or can take it.
While it is certainly nice to have a 5.1 Surround system, depending on budget and needs, perhaps a Stereo system would be a better choice. You get more for a fixed budget, though fewer features.
Any modern AV Receiver above a certain minimum standard is going to have Network Streaming. From that you will be able to stream music from your computer and from the Internet. There are also Stereo Amps that have Network Streaming built in.
So, in addition to the Dimensions of the room, we are going to need a working budget. If the budget is low, then I absolutely think a Stereo needs to be considered. If the budget and space are sufficient, then a Surround Sound can be considered.
Answer those questions and we will have a starting point.
Steve/bluewizard