Building a PC specifically for Dolphin

[Starscream]

You'll need an extra core for the LLE audio back-end, it uses a core. The video card is a bit overkill, but since you're not worried about the money, having a great video card will be good for Dolphin and for anything else that you might do on the PC (PC gaming). Dolphin will not use 8GB of RAM, but with a PC like that, it just make sense to have at least 8GB (in my opinion). As far as the Windows over Linux question, Windows runs Dolphin generally better (debatable I guess) than Linux and you will be able to use DX9, DX11 and OpenGL whereas Linux will only be able to use OpenGL.