I think that it is enough for one S5 without OC... It depends how hot are those pcie cables that are connected to miner...
Discolored one connector on the miner to a lovely 'caramel' ... (the S3 I took off the Thermaltake today after not being able to touch for more than 3 seconds)
This one didn't have any crumbling wires or PCIe's (yet)
Got this one licked and am going to stay with Corsair/EVGA/Rosewill's ... NOW the infernal howling of these fans needs to stop ;-)