compatible mobo for I7 6800

1) http://uk.pcpartpicker.com/product/Q9Gj4D/asus-motherboard-z170a

That's a pretty good board, though may want to change the color scheme for DDR4 memory etc (I guess make it black, and since the case is WHITE the above board should work fine)

2) I strongly recommend against a FOUNDERS edition of GTX1070.

A 2-fan Asus, EVGA or similar card would be better though you may need to WAIT several weeks for prices/stock to get sorted out (price gouging due to supply/demand)

3) SOUND. I'm not sure if that sound card is much different from the onboard audio.

4) I suggest an HDD as well if you don't have one. Maybe a 1TB WD Blue.