I agree 100%. With Macs, the best GPU you can get is ATI 5870. That's not that good anymore.
If I were building a gaming PC, the maximum I would spend would be 2000$. Anything over that starts to be useless because 1) games can't take advantage of the faster hardware 2) everything is already maxed out with good FPS. You don't get much bang for the extra bucks anymore. Save the money for future upgrades.
Furthermore, as you're spending thousands on a gaming computer, remember that you need a monitor with 2560xSomething resolution. It's nothing else but ridiculous to spend thousands on the computer and then use a 20" monitor. You need the 2560xSomething to take advantage of your hardware. Otherwise you could just get a budget PC for 1000$ as it would run all games maxed out on that 20" monitor.
All in all, if gaming is your main thing, then don't think about Macs, especially not the 12-core MP. If you seriously want a Mac, then 3.2GHz quad with 5870 is the best choice IMO. A PC is still a lot better choice though
This!! Dear god! This! On everything I agree; EXCEPT the 2560xsomething... a 1920x1200 or 1920x1080 monitor is also fine...