Will this build work?

Hm, i'm kinda new in PC hardware, so i have to ask, why does everyone keep advising dual channel mode for RAM? I mean, in all the benchmarks i've seen, dual vs single channel memory difference is negligible at best, and if you buy 1x8gb ram instead of 2x4gb ram, you would be able to upgrade more ram in the future...
 


Also for me the single stick is cheaper and I'm on a tight budget.