Monitors are getting cheap nowadays.  I've seen  22" LCD screens go for as low as $150 bucks at the local electronics store, and I'm sure they're going to get a lot bigger and cheaper...

So how many is enough?  

How many is practical for the average trader? 14 monitors... 10.... 5? I've had up to six 20" monitors, at one point and generally found myself turning off my other monitors, till I was left with three.  And even with the third monitor, I'm not trading on it. I'm usually playing a game, chatting on Ircforex, surfing the net, or watching porn...

What eventually starts to happen when you have such a massive setup, is that you start getting "traders neck" -sort of similar to tennis elbow. Try shaking your head for three to eight hours a day, and tell me how that goes... You're seated, and constantly turning your neck, glancing across your screens, trying to focus on your EUR/USD chart on your sixth monitor, to the far upper right, while you're trying to setup your trade on the your execution platform on your first monitor, at the bottom left corner. You decide to execute that EUR/USD trade, just to realize you were actually looking at a USD/CHF chart.. ¡Doh!

Soo... go out and buy yourself two or three 22" or 24" LCD screens.

Now a multi-projector setup... That would be uber-l33t!