Upgrade MSI x58 pro + i7 920

Jun 14, 2018
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Hello everybody! I'm about to upgrade my computer. I only want to upgrade to the motherboard, ddr and processor memories. Currently I have MSI X58 pro, i7 920, Asus Strix GTX960, 12 gb ddr3 663mhz and segate hybrid hdd. The source is silver of 550w. I just want to upgrade my motherboard, processor and ram memory.
My budget is up to $ 600. I would like to know what would be the best upgrade, considering that in the future I would like to change the GTX960 with the GTX 1070. I do not want to buy a very expensive processor but to be pulled down by the future card graphics card 1070. What cpu i need to buy? I was thinking of an 8700k i7, but I think it's too much ... Thenk you!