Just build your own, its easier to put together a computer then people who havent put one together think
You do realize that when ASIC's are a reality, and that will happen, FGPU's and GPU mining will be no good anymore since the difficulty will be increased so high that they are unable to be used, just like what happened to CPU mining.
So my point is, I would not spend the money to build a kick ass box right now, only to see it become obsolete and useless for mining inside of a year.