With modding you can fit two 420mm's, i've not personally tried two 420's so IDK but it's possible. I would buy the case and then see what will fit, the holes are there for a 420mm.
i had a 750D had a EK XTX 360 in the roof, now my mate has it and he has a 30mm 420 in there.
from what i remember i think it just about fits, but the fins on the 5.25" bay may stop you from going 45mm if not just cut the fins out and you should be fine