Performance/gaming-wise, can 2x gtx 560Ms outperform a single gtx 570m? (without taking into account other performance-related factors like processor, RAM, etc). I am at a dilemma as to choose gtx 570M or 2x gtx 560Ms for my customized gaming laptop.
560m SLI will outperform 580m, however that is assuming the drivers and the application supports it (more problematic in laptps than in desktops).
Also, you need to factor in the heat. That is the main problem of gaming laptops as it will throttle down the gpus/cpu if need be.
One thing to note thou: 560m SLI still wont give you playable framerates at the mos demanding games in full hd maxed settings (metro 2033 for example), while both 570m and sli 560m will give you playable framerates at high settings in games like metro 2033, and very high settings in less demanding games.
For laptop cooler (i assume you will have at least 17 inch laptop), i would suggest one of the following:
Thermaltake massive LX/ST 23 or Cm Storm (this one requires a power socket). I suggest you google those to have a look.
I heard the XZXT Cryo is a very good one, but i could not test it myslef.
I did test others (lian li, zalman among others) and they basicly are useless most times.
Another option (im going for this one) is getting some 12V fans, a USB conector, a 5v to 12v exchanger and making a custom cooler . Or even use them on 5v mode (schyte gentle thypoon in my case).