I have 7 of these 12/13 GPU rigs in the farm and .... yes it is fun building these rigs but you need plenty of power for them and well ventilated. All of them are with the Deltas 2400w and housed in the center of the farm so that I can use the air extractor on them during the hot days. These rigs are the hottest in terms of temps and hash power. Ironically these rigs are the only ones that are hanging like bats and since they are stable, they will likely remain with risers. Multiple 8 x GPU riserless rigs are ideal for density and can fully populate open cage metal racks and make use the of floor fans effectively. I dont forsee doing anymore AMD rigs (exception of the Vega rigs) because the NVIDIAs are a blessing - always works, easy to control voltage and very stable in most cases.

So lessons learnt - the bigger the rigs, the bigger the issues in PSU requirements, cooling strategy, cabling, stabilizing them.... a golden rule : stability, cool temps and consistent submission of shares to the pool's stratum server are more important than achieving the meanest powerful, fastest rigs that requires constant babysitting. If you have a large farm -- undervolting is very very key - forget the world GPU speed record.