Complex sentence: The Vs. System was designed primarily as a kit to retrofit "Donkey Kong", "Donkey Kong Jr.", "Popeye", and "Mario Bros." machines; as such, they require the same special monitor that these coin-ops used.
Split into simpler sentences: The Vs. System was designed primarily as a kit to retrofit "Donkey Kong", "Donkey Kong Jr.", "Popeye", and "Mario Bros." machines. Being as such, they require the same special monitor that these coin-ops used.