A little late, long time lurker; new registeree, but I mine loki(cn heavy) with 2  r9 290x(trix, 3fan version) i get about 540-560 h/s stock clocks(1000core, 1300 mem) and about 600-620 h/s overclocked to (1060core, 1500 mem) runs stable @<65°c ambient temp 21°c ≈ 70°f.  And about 55°c with AC ambient temp 60°f.  I know the 290x have 4 more compute units than the 290, and u can unlock them in many 290s if they are only software locked, and from what I hear it isnt too intensive. Theres a progran that checks if theyre unlockable. Note: Undervolted core Voltage to 1075mV, and left mem alone. The 2 gpus and system is pulling ≈ 425ish watts from the wall.