If you want dual 660M+ (even a 680M) get an Alienware M18X which is around a 12 pound computer while the rMBP is 4.5. Games won't run as well, but is a great card (even factory overclocked so it is comprable to a 660M) for the computer.
There is a big 'ol gray area between rMBP and M18x. The perfect middle ground is the Lenovo Y500. It's about as heavy as a cMBP, offers a 1920x1080 screen, and dual GeForce 650M/750M GPUs.