If the case only has USB 2.0 ports on its front panel then it's an older design. What motherboard brand and model will be used in this computer case?
The 620 Watt power supply that is included with the case, I'm assuming, is the MODECOM MC 620 CARBON that has a maximum combined +12 Volt continuous current rating of 39 Amps and has one 6-pin and one (6+2)-pin PCI Express supplementary power connectors.