I just want to say, that it is NOT true, that this case is limited to a 240mm radiator. I have put a Corsair Hydro Series H115i even with push/pull configuration into my case easily. Its even stated in the manual. If you dont believe, go here: http://www.coolermaster.com/case/lan-box/haf-xb/ and download the manual and read for yourself.
But there are downsides. CoolerMaster did some little things very bad. To offer the biggest freedom, they included mounting holes for either 2x120 fans or 2x140 fans for the front, which is the only place for the radiator. This first sounds good, but if you decide to go 2x140 with a 280mm radiator, those useless mounting holes for the 120 fans, will cover quite a lot space from the radiator. I have cutted them out
.
If you want to go the 280mm route, you need to be careful with only one thing:
The length of your graphics card. Lets say you have a card with 250mm in length, then you will have 82mm "room" to the front, so you can use a radiator with a maximum "thickness" of 57mm + a standard 25mm thick fan, for a push/pull scenario or a maximum "thickness" of a 82mm radiator with a pull scenario. The manual recommends exhaust airflow for the front, if a radiator is used.
My setup is the following:
1. 230x200x30mm BitFenix Spectre Pro for the top. Huge PWM fan, that covers nearly the whole mainboard, used in exhaust mode.
2. 4x 140mm fans in push/pull for the 280mm radiator, also in exhaust mode.
I have no intake fans at all in my case and you dont need one, because one of the biggest advantages of this case, are the many and huge holes the case have. The case is best described like a hybrid lanbox/benchmarktable.
It cools a i7 6950x@4,3 Ghz at 55c max while gaming, a little more while heavy working (summertime 30c +).
I can go higher, but its pointless for this CPU, because it consumes way to much power for each Ghz above 4,3 Ghz.
PS: if you buy this case, do yourself a favor and by proper dust covers. I highly recommend the Demciflex. They even have a perfect fit setup for the HAF model.