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If that's all he plays it would be a massive waste of money to upgrade from a Vega 64 at 1080p. It won't make him floss any quicker.
He wants a 240hz monitor next so wants to push fps as high as possible. It's his birthday in a few months so a GPU upgrade was something I was considering and then a monitor at a later date. He currently has a Ryzen 2600 but I'm upgrading to a 3900X and will donate him my current 3700X shortly. That will probably give him a boost anyway.That must be pushing 140 plus frames as is anyway, what is his cpu?