Dell 3008WFP 30 inch UltraSharp Widescreen Monitor ($1,500)
Once you play on a 30" monitor, you will never, and I mean never, go back to anything smaller. It will change your gaming experience and make you a better and smarter person (also, you will be more attractive). Oh, you'll also be poor because the video cards you need to run these things are brutally expensive. That's OK though; no one said addiction was cheap.
Poor is right! If you can't afford to bring home the ultra-expensive Dell, try the slightly-smaller ASUS VK266H 26-inch full-HD monitor on for size — it's only $330.