So my friend asked me for help on upgrading his prebuilt PC, which is an Acer Aspire TC-780. It has an i7-6700 3.4 GHz quad core, 8GB of DDR4 RAM, and one PCI Express x16 port. He asked me what GPU he should get (he wants to play PUBG, for reference. I have an i5 with a GTX 1050 and I get moderate frames).