Pricerange?
Honestly, what you're looking for is any monitor under 5ms response time with any advertised resolution 10000:1 or greater, and resolution of 1920x1080 and he'll be happy. Just be sure the video card in the computer can pull that resolution off or his games will chug.
If you really care about color quality, look at the Viewsonic line like the new ViewSonic VX2739wm. Samsung always does good with their montiors as well, but pay attention as they have way to many fucking models.
Acer and LG are good monitors for the price, but generally do not do great on color. But of course, its really how well your son is going to notice that something isn't as orange as it should be
As an avid PC gamer, feel free to ICQ or email me on any you're considering and I'd be happy to give you feedback on it.