How to power the Bitmain Antminer C1?
AntMiner C1 Manual:


  You must prepare your own ATX Power Supply. There are 4 PCI-e connectors for +12V DC 
  input and all are required.


That either means:


The manual is right, and some of these are not 12V connectors. This seems unlikely.
The manual is wrong, and you need eight 6-pin PCI-e connectors.



  Is it possible to use two or more PSU's to power the miner? 


It depends on how they designed the miner. Those connectors might join together inside the miner, which would mean that you'd want one power supply, or they might be two separate circuits, which would mean it would be more or less safe. Generally, you don't want to use two power supplies to power the same part, though. Can you take a picture of those connectors with the case off?

As for the power supply recommendation - power supplies with eight PCI-e are very expensive, primarily because nobody needs that many. I mean, a typical desktop computer is probably going to need one PCI-e connector. They do exist, though.

However, I would recommend getting two power supplies with four PCIe connectors. I suggest the Cooler Master G650M.

Oh, and the manual says this, which suggests that it's not water-cooled out of the box:


  Cooling kit is not included in C1, please read the instruction at www.bitmaintech.com to 
  buy them.