Server PSUs - good solution?

Conventional ATX power supplies are quite expensive - especially when trying to power 6+ GPUs - about $300 for an EVGA 1200W.

Server power supplies such as HP 1200W ones are pretty cheap in comparison - about $70 USD.

I know that with a server PSU you need a breakout board, but these don't seem to be able to power the motherboard as the only ones I can find have only PCIE connectors for connecting to the GPUs.

Is anyone using a server PSU for their rigs - and how have you got it setup? Or any advice on not using a server PSU?