Hopefully the reference clocks as well as the aftermarket ones then and isn't too loud then
I'm thinking the reference one is probably limited, stock at 1266Mhz is should still do 1400 - 1500Mhz but AIB's with better coolers and more power would clock better.
2304 Shaders @ 1266Mhz rumoured Fury-Nano performance makes perfect sense to me, its 'at least' 390X performance but GCN 4 has a lot of enhancements over GCN 1.2
Performance wise i think the reference ones should clock to 980TI - Titan-X.
AIB ones, beyond that.