I am planing on buying an SSD to my laptop (Acer VN7-791G). My laptop has only 1 SATA port and 1 M.2 slot. Is it better to just buy a SATA 3 ssd (850 evo or extreme pro) replace the hdd or buy a 850 evo m.2 and still use the HDD (5400 rpm)? No problem for the space, i care more about the performance of the pc.