"best results" and "good enough" are two very different things. Most of us can 5 box fine on a quad core chip, so even though we can't dedicate a core per wow client, we manage. I'm sure we would all love a mainstream 6 core chip, but I don't think intel has any plans to do so. Maybe once LGA2011 has 8 core flagship chips, the 6 core will drop in price.

I run all of mine on "fair" and run fine, I still have lots of lua errors from other addons I am too lazy to update, but it runs good enough for the time being. I have a GTX 570 and have run into VRAM issues, so I think whatever card you get, get it with 2GB+ of vram. My next card is going to be 4GB.