I don't think he's replying directly to your comment but asking for your guess/prediction as to what could plausibly fit in a box that size.
Ah... well, then.
For starters, we're looking at a box that is essentially half of a 360 slim. The chips have to go underneath the drive as well, which will be a source for heat. Whether it's significant or not would be irrelevant considering the tighter confines and the reduction in air flow space.
Also keep in mind that the 360 Slim had a pretty huge heatsink block with a fan that blows directly out of the case. The thing can get pretty hot still too.
I'd look at mobile GPUs directly, but they only list TDP, not the actual power consumption, and that's not to say that cooling is actually good. One of the console requirements is that the box not sound crazy. Well, high end mobile GPUs and CPUs when running at load are going to be awfully loud in a laptop. My own 17" is pretty freaking loud and it's not even top-of-the-line (Core i7 Q720, Mobility 4650). So where do you draw the line? The thing has heating problems with less than 2 hours of straight up gaming - and the games I play don't even stress the 8 threads let alone four.
I think it's easier and better to do this prediction stuff by process of elimination rather than just spewing guesses based on active power consumption or perhaps even TDP or naively choosing the hottest hardware that fits into a laptop. Mind you, laptops have more complex cooling designs than just your run-of-the-mill heatsink and fan.