Server PSUs are the best choice when you are able to DIY and source cheap components. A fully DIY wired PSU w/Pico will cost ~85-100$ in material (DPS-1200FB), labor cost - YMMV.
Frankly DIY seems to be not your case, so better stick with ATX power supplies.
You'll find cheap breakout boards only for DPS-1200FB and the likes. Because they are Chinese.
There exist breakout boards for beefier power supplies - DPS-2000BB, IBM 2980W, etc. They cost >40 USD.
Link:
http://www.gekkoscience.com/products/IBM2K_board.htmlI will reiterate - if you feel unsure to modify server PSUs, go for decent ATX PSUs.
modification is not a problem, I have also a friend who is electronics technician and he can do the work for me for free. The problem is that pico psu is as expensive as a separate cheap psu for the motherboard and also the pci-e cables/plugs for the breakout boards also cost a lot. Do you also have any source where I can get just the 6+2 plugs and the wires separately cheaper than the ready made ones from ebay? For 17 rigs this will cut down a lot of the cost.