650m Sli, 750m or 840m

[somethingpeople]

I was looking at gaming laptops in my budget and the only ones that i could find were the 650m sli, 750m and 840m. All of the cpus were decent i7's but I need to know what one out of all of these are the best and if it is good enough to run modern games on medium settings. (They all have 8gb ram and 1920x1080 displays)

 

[Doomalikaw99]

650m sli!