On the GPU side of things, an Nvidia GeForce GTX 960 or AMD Radeon RX 470 provide enough pixel pushing power to meet the Call of Duty Modern Warfare 2 minimum specs.
More modern GPUs should provide a smoother frame rate, and developer Infinity Ward suggests slotting at least the Nvidia GeForce GTX 1060 or AMD Radeon RX 580 into your PC.