In Australia I got a laptop with quad core i7 4700MQ, Nvidia 740m, 8GB of RAM and disc drive for $600 Australian nearly a year and a half ago. For gaming I wouldn't go anything less than an i7 with 740m or 840m and 8GB of RAM.
For AMD I would want one of the best A8s or an A10 laptop at that price with R7 or at least m8670 graphics.
So the Lenovo is by far the best option if you can afford the parts I recommend. The other two are a bit too weak for gaming.