Before going this route, I'd check Dell's Outlet for equivalent model... likely to save $1,000 or more.... in case that matters.
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.
Yes, that is the correct process. Many who think they want an 8-monitor rig want to buy an el-cheapo computer first. Often/usually doesn't work like they expect. Rather than 8-monitors, why not try to use 4 larger ones? Lots easier logistically all around. One could run 4, 24"-28" or even 30" monitors and have ACRES of display area.