I've heard that one, too. I don't get the concept of gaming and listening to music. Then, I play mostly first-person shooters and not being able to clearly hear your surroundings is a great way to get killed.
Oh, I love when people cite that study. The reason being they usually get it wrong. The study is often cited as claiming more monitors increase productivity when what the study actually says is more screen space. When asked to clarify later the guy who did the study said, "No, more monitors don't make you more efficient. In fact, after a certain point it has a drastically detrimental effect. The ideal amount of space for the majority of people is 2560x1440 on a 27" to 30" screen."
Of course, it all depends on usage cases and individual tastes. If you're a video editor, for example, it's very difficult to get buy with just one screen and most tend to have at least one screen for their work and another just for viewing the output.
The cheaper Dell IPS screens run around $300 or so last I saw. They're not quite as good as their more expensive brethren but any IPS screen is going to be better than your typical non-IPS. They are faster, use less energy and have brighter, more accurate color representation. If you ever want to know the difference between a non-IPS screen and an IPS screen, look at the iPhone 4. They use IPS screens and are regarded as the best you can find on a phone. (Of course, no IPS display you're going to buy is going to have anywhere near the pixel density of an iPhone 4.)
