One Big Monitor? Or Mulitple Smaller monitors?

I am trying to set up a workspace on a budget, I have a Macbook pro 15” (not unibody), and use it mostly for photo editing with lightroom and website stuff, (Dreamweaver, Flash, Photoshop etc)

What kind of monitor setup better lends itself to this type of work? I am trying to keep it under $200, so I can get a nice 23” I think, but is this the way you would go? What is your workspace setup like?

Thanks.