I buy most (practically all) of my PC parts either from newegg or Amazon. Amazon has much better return policy than newegg (a negative about newegg). I've never purchased anything from Outlet PC so I don't know how they are.
When I built my last desktop DAW system, I got the motherboard, CPU, power supply and cooler from Amazon. The BeQuiet case and Corsair memory from newegg. I reused a Samsung EVO 850 (500GB) SSD and 2TB hard drive, Monitor, and wireless Keyboard and Mouse from my old DAW desktop. I'm not using a separate video card.