The Corsair AX1200 power supply is an absolute monster PSU, coming in at 1200w of power and a clear inch bigger than the size common to "normal" power supplies. This baby has some very impressive features so when I was building a monster gaming PC with one in I decided to showcase it. Take a look at the video. It will give you a sense of the scale of this huge power brick. You can't fit one in a small case and I wouldn't even attempt it in some of the smaller ATX cases.
The power supply is fully modular. As you will see from the video it comes with a huge number of cables. I know not everyone will use them but its nice to see them not being tight with these.