you have to reconsider your setup. 860W producing 1272 MHash/s

that's not very efficient. my current system draws 240W and produces 385 MHash/s. it's not some cheap low power consumption cpu, either. it's an overclocked 2600k. in addition to that i use a 2nd video card for gaming etc, which is (of course in low power state) included in the 240W.

 

My rigs: 1.48 MH/s/watt + no AC cost
Your rigs: 1.60 MH/s/watt + maybe some AC cost

Clearly your rigs are more efficient.  My GPUs are overclocked, perhaps yours is not.  In any case, I had limited choices when purchasing my rigs and chose the Sapphire HD 5770 because of their low purchase cost for the MH/sec produced - by then the 5830's were gone.

 

user@linuxcoin02:~$ DISPLAY=:0.0 aticonfig --odgt --adapter=all

Adapter 0 - ATI Radeon HD 5700 Series
Sensor 0: Temperature - 65.00 C

Adapter 1 - ATI Radeon HD 5700 Series
Sensor 0: Temperature - 56.00 C

user@linuxcoin02:~$ DISPLAY=:0.0 aticonfig --odgc --adapter=all

Adapter 0 - ATI Radeon HD 5700 Series
Core (MHz)    Memory (MHz)
Current Clocks :    960           1200
Current Peak :    960           1200
Configurable Peak Range : [500-960]     [1200-1445]
GPU load :    99%

Adapter 1 - ATI Radeon HD 5700 Series
Core (MHz)    Memory (MHz)
Current Clocks :    960           1200
Current Peak :    960           1200
Configurable Peak Range : [500-960]     [1200-1445]
GPU load :    99%

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