Hey, I'm new here.
first off, Mac aren't really gaming machines. if you're a gamer, you can build one to your needs for much cheaper, and it would blow just about any Mac away. Now, I'm typing from my little Mac Mini here and although I do 'game' on it per-se, the games aren't exactly hardcore. Macs hardware, operating system and general configuration is more geared towards workstation tasks {especially the Pro} like multimedia work, which is really what the Macs are hailed for anyway.
There is really no point in my eyes in buying a Mac with a Core2Extreme, as a core2extreme is essentially a high end core2duo with the multi unlocked. However, an unlocked multi means virtually nothing in a mac where theres little to none overclocking possibility. So you pay for some extra MHz and thats it.
Also, the Apple mighty mouses would most likely be horrible for games. Luckily we have a store nearby, so I went in and tried one. I found myself leaning over on one side of my body to try and get the right click. Crazy.
Final rule with Macs, in my opinion, is buy one that's bottom line and upgrade HD and RAM yourself. Ultimate win.
What kind of games are you expecting to play? If its going to primarily be for games, this is NOT for you. If like me, you will mix general use in with some light gaming, then go for it. The Mac OS is a dream to use.
Hope this helps.