Do you have a 144Hz monitor or a 1440p+ monitor? If yes, then go Crossfire. If you have a single 1080p monitor then no upgrade needed. If a single 1440p monitor then get the 390x, not 390.
Do you have a 144Hz monitor or a 1440p+ monitor? If yes, then go Crossfire. If you have a single 1080p monitor then no upgrade needed. If a single 1440p monitor then get the 390x, not 390.