Your setup computes 1.71 Mhash/Joule. Although there is a lot of invalid data in
https://en.bitcoin.it/wiki/Mining_hardware_comparison your claim is inconsistent with the wiki which puts the value anywhere between 1.3 and 1.6 Mhash/Joule.
How did you measure 650W? Do you under/overclock the GPU or memory? Etc.
You mentioned 5830s so I picked that rigs as an example. 1.71 isn't even my most effecient rig.
You have a farm. Are you saying you can't pull off 1.71 Mhash/Joule on any of your systems? Who cares what the wiki says. The wiki is old and outdated.
1. Buy quality parts. 60% efficient power supplies are stupid.
2. Plug system into Killawatt meter.
3. Use latest mining software and optimize hashing parameters.
4. Overclock core speed and underclock memory speed.
5. Keep fans clean so nothing overheats.
There's no rocket science here. Just basic mining optimizations that any half-decent miner would do.