Thanks gmay3, ya I've got the connection made on the ATX, i've used an ATX as a power supply before so was expecting to need to do so.

Yes, TopJimmyCooks, I've got 11A and 5A wired up as described ( I'll attach a picture later). No LCD or LED lights when I plug in my usb cable to either of my Macs, I do get a "USB Device is drawing too much power" warning, and the ramps board does not show up on my list of USB devices.