-Motherboard seems just fine
-You'll need one x1 to x16 USB riser for 2 graphics cards (one will be plugged in at x16 and one will be plugged in at the riser)
-Processor seems fine
-Hard drive is fine
-RAM is fine
-PSU is useless. Throw it and buy a new one with 1000 watts power supply.
-Those 2 GPU's should work just fine on this built (after the required changes)
-Complete upgrade isn't required
-No, go with 2 GTX 1080
2 gtx 1080 is better than 2 asus strix rog 1080 TI oc version ?
As 1080 is only 8 gb and 1080 ti is 11 gb or my motherboard doesn't support 11gb ?
Even my mining speed will be slow with 8gb when compared to 11 gb ?