Quote from mgookin:
It looks like OP is confusing qty of cpu cores to qty of monitors. Ignore cpu and look at gpu.
If you want an 8 monitor system, start your design at the monitors. What size & resolution? Then find GPU's that will push them. Then find a mobo that will hold those GPU's. Then find a power supply for all of that. Then find any quad core 3.0gHz cpu. then find your case, fans, drives, etc.