As long as your PSU has 6+2pin and 6pin then you should go for the r9 390x, it's the better choice. However either list full PSU model so I can give you that info, or make sure for yourself. But the 390x is the more powerful choice.
As long as your PSU has 6+2pin and 6pin then you should go for the r9 390x, it's the better choice. However either list full PSU model so I can give you that info, or make sure for yourself. But the 390x is the more powerful choice.