Yes it is true that CPU is not a limiting factor in gaming, as long as you have enough GPU.
And while the I3 is very energy efficient, it seems silly to buy a built in GPU for a gamming system that will never be used. Unless I'm wrong and both it and a card can be used together. That might be nice.
Also, instead of going $15 cheaper for the X3 chip, you could have gone just $11 more than the I3 and gotten a AMD Phenom II X4 940 Black Edition at 3.0GHz. Very overclockable from what I've read.