2 screens minimum.
I use 2 MacBook pro's both dedicated trading computers, with an extra screen each. One stays on 24/5 , other only during trades. Both hooked to dsl and cable.
1 Mac air for streaming news, mail, analysis and searches.
A secondary Mac air back up tethered to an iPhone and another iPhone with the mobile app running.
That's in my trading room.
One more laptop in the living room.
My risk management.
life's too short for boring cars and cheap wine.