Arduino Uno, high torque DC servo motor and ATX power supply

You MAY be able to get away with using the 5V from the PSU.
Connection data isnt shown.

Spec for a similar servo motor:

No. Operat voltage: 6V;8.4V
4.1 Idle current: 5mA; 5mA
4.2 No load speed: 0.17sec/60°;0.13sec/60°
4.3 Runnig current: 400mA;510mA
4.4 Peak stall torque: 58.5kg.cm;70kg.cm
4.5 Stall current: 8.5A±10%;10.4A±10%
4.6 Working voltage range: 4.8-8.4V