It depends, on how these Pis should work together.
If they work together only loosely coupled, it might be the best to use a simple power strip and 10 independent usb chargers, each with at least 2.5A current (about 12W). If one of the chargers dies, only one of your Pis can't work on, but the other 9 will work happily as if nothing has happened. Redundancy is great with these.
If they are tightly coupled, you have no advantage using 10 independent chargers, because if one Pi stops working, the other 9 cannot do anything without it. With such a configuration (and may even be in general), I would recommend using a big 5V PSU with 125W or more (like this beauty, but you can get them even much much bigger) , and solder 10 USB charger cables to connect to the Pis. Such a 5V PSU is much easier to keep cool with a small fan, and big power adapters are usually much more robust than their little plugin counterparts. And cheaper as well, in terms of $/W.
I would not recommend a standard ATX PSU, because they need a consumer also on the 12V lines.