There is no best system.
Of the components:
The best amplifier is the 5000 - unless you have active speakers in which case it is the 7000.
The best CD player is the CD5500 (the CD50 is far too unreliable , and is simply too weird - a single channel DAC!?? - the fact that hardly two are the same design)
The best cassette player is the 5000 - unless you really want auto-reverse.
The best remote is the 7000 - as long as you have a Beomaster 6500 or 7000.
The best record player is the 5000 - best made and best sounding. The tangential ones are more convenient.
Of course the best stacking system really is the Beolab 5000 system of 1967!