Normally, you would get somebody in to help you with this, because as others have mentioned it's non-trivial. You need to be especially careful with high currents, the same as with high voltages.
As Szymon suggested, perhaps the included PSUs are not the best way to go - they are generally not as efficient as an industrial supply operating at its rated load. Additionally, power strip ratings are generally optimistic, and they are not manufactured with great precision). Do not daisy chain your power strips, ever. Maybe investigate having a custom power system built that will feed your routers?
@Olin, while I would agree that the worst case is the ideal case to use for sizing of system components, in practice determining the worst case is very difficult. Current ratings on components are there to keep the devices (be they power strips or FETs) inside safe thermal limits. Your building's cabling is rated based on the expected heat rise in the conductors for a given load. Almost all building systems are sized based on average load (transients can be ignored because they do not provide a significant heating effect on the cables). Of course, determining average load is the hard part. If it were not this way, you could never cable an office block where people all come in and turn on there computers in the morning...
For the purposes of answering the question, average load could easily be measured using a multimeter on the 12V side and watching the current for a few minutes. (You could use a datalogger if you are so inclined, but it's probably overkill). Then multiply this number (say 1.5A@12V) by the number of devices you wish to power and you'll end up at a magic number of 150A@12V or so. I doubt your routers with the radios off will draw anywhere near that current, btw.
Then you need to check that your building can supply the required current where you need it (say 20A@110V, 10A@230V). You will need a dedicated AC circuit for this project.