the 7750 gets all its power through the pcie16x lane which is able to supply up to 75w. your i3-530 in the gateway has a tdp of 73w. with the 300w power supply you should have more than enough wattage headroom to run the 7750.
the 7750 gets all its power through the pcie16x lane which is able to supply up to 75w. your i3-530 in the gateway has a tdp of 73w. with the 300w power supply you should have more than enough wattage headroom to run the 7750.