As long as you use an ITX or mATX setup in the Cerberus-X, you shouldn't have a problem fitting a 280mm rad + standard fans on the bottom (like an NZXT x62 setup).
Note: The x62/x52 pump-over-processor solution, as RGB and awesome as it may be, is about 4mm too tall to mount an ATX PSU over it. If you go that route, be sure to pick up an SFX PSU instead (mounted at the rear with the optional adapter or at the front).
However, with an standard ATX board installed, the 280mm rad+fans will hit/block all the connecting i/o at the bottom of the motherboard. By my measurements, I could fit the 280mm rad but then I would have to scour the earth for some 10mm fans that would provide awful cooling so in the end it's just not worth it. Therefore, a 240mm rad is required (stress: 280mm won't work) at the bottom in this type of setup.
That being said, if you have a standard length GPU (as long as the width of an ATX Mobo itself) you shouldn't have any issues fitting the 280mm rad+25mm fans at the front (with an ATX-sized PSU at the rear obv).
For the best temps possible, this means it could comfortably fit a 240mm rad at the bottom and a 280mm rad at the front if you're planning a dual-rad setup.
I know this has all been stated before but I just wanted to reiterate as people are starting to get their cases.
With that out of the way, I'm done Tetris-ing for the day. I will report back once the replacement parts arrive.