If, as in the picture you offer as a reference, you are using either a BeoSystem 1 or BeoSystem 3 as the surround sound processor, you would simply track down a single BeoLab 4 and connect it to the Center channel input on the processor.
If, however, you intend to run the sound directly out of the BeoCenter 2 (as the quote implies), you will not be able to accomplish this. The powerlink output of the BeoCenter 2 is stereo only. What you see in this picture is the BeoCenter 2 being used as both an audio master and a connected DVD player with a BeoSystem (the eye there below the screen is evidence). That is the only way to process multi-channel sound. Otherwise the speaker would just be an extra right or left channel and sound awful.
There is scarcely anything in this world that some man cannot make a little worse and sell a little more cheaply. The person who buys on price alone is this man's lawful prey. - John Ruskin