What do the R9 300-Series actually consume in terms of wattage, here you go - AMD Radeon R9 390X, R9 380 And R7 370 Power consumption stress tests. : r/pcmasterrace
Performance Benchmarks : ASUS Strix Radeon R7 370 and R9 380 reviewed: New cards for the mainstream (Updated) - HardwareZone.com.sg