I've only bought Workstation class for my work. For that, I only buy Lenovo ThinkPads (w/ full warranty from IBM). I love their keyboards.
For Gaming, I would assume Alienware (which is owned by Dell) is great. Lenovo has gaming stuff now as well.
I'm not a computer 'geek', but is seems the throwaway Gaming computers are the better buy compared to buying Workstation class computers. Most programs run DirectX now and you don't need OpenGL.