I'm currently using a Quad monitor set up. 3x +1
I love it. Great functionality and multitasking. Great while gaming in eyefinity and still being able to keep your monitoring and communications programs visible.
But when not gaming I really only tend to use 2 monitors. Occasionally I'll use all the monitors to do stuff but it's rare.
I'd say go with quad if your finances allow for it. You won't be disappointed and I've never complained to myself that I've had "too much"...