Is my system only as good as its weakest link?
This notion is nonsense.
In fact, the playback system does not behave as a chain at all. Sure, a chain of events needs to take place to get sound out, but really it's a system and must be approached systematically. That's why we call them: “Loudspeaker System,” “Playback System,” “Sound System.”
Like any complex system, the playback rig and its environment cannot be fully modeled without an understanding of its components, relationships, and acoustics. But this is not to say that evaluating devices sonically can only be done by those few with profound understanding- anyone can.
Check out How do I evaluate changes in my playback system? for additional insight.