I currently run a single Asus Strix RX 480 but want to add another one . I'm using the Raidmax Vampire 700w Modular 80+ Gold . Would it be sufficient enough ? This vampire series seems like it's on the higher end side of the Raidmax brand . Thanks !
Raidmax is a pretty bad brand, but if this is your PSU's model number: RX-700GH, it may be okay.
I'm not sure you'd really want to crossfire on it, or crossfire at all, as you run into more problems than performance increases with multiGPU configs.