that would be grossly incorrect good sir.
A single stick of 8GB is not only not enough RAM to handle more modern AAA titles and newer ones to come, and it's single channel which will hurt the CPU performance significantly which will severely hold back the GPU performance and hurt the frame rates. Making spending all that money on a 1070 a waste.
From what I can tell, you decided to sacrifice amount of RAM, quality in motherboard, quality in SSD, lower HDD size, and chose a much cheaper quality PSU just to slap a GTX 1070 in there.
This is not good PC build practice and is overall not a good allocation of funds.
If you are going to go with a cheaper SSD, then ADATA is the way to go, not the BX500.
Corsair CXM power supplies are bad. While you can get lucky on occasion and get one that was good, like 90% of them are just bad.
The microATX board is of lower quality and can't handle overclocking the CPU hardly at all. Like maybe up to 3.6Ghz but that's about it.
Not trying to bash on you or bring you down. Just trying to better inform you so you can have a better understanding of what it is you are putting into a system.
Also, no. You CANNOT just add another stick of RAM later on.
This is bad because there is no guarantee that the RAM will work together since they didn't come in the same kit.
So it ends up being a gamble if the two sticks will even work together at all and if they don't then the buyer is screwed out of the money they just spent on that second stick.
And your claim about it performing 35-40% faster than a GTX 1060 I can only say is in regards to the GPU's compared to each other by themselves and not for the system as a whole due to the things I've mentioned above about single channel RAM and the overclocking potential of that motherboard along with the fact that overclocking potential is heavily attributed to RAM as well and single channel just ain't gonna cut it.
Please, for your own sake and the sake of others you plan on giving component buying suggestions too, do some research and learn some more about how these things work before you end up convincing someone to spend their money on something that ends up being not worth the money they spent.
And again, don't take this the wrong way. I just feel you have a bit of learning to do is all so that you can become better at build suggestions and more knowledgeable in PC hardware so that you can be better equipped to help others, especially when it involves telling them what to spend a large amount of money on.