well... the HAF X does have one 200mm top mounted fan and room for a second. So although this is a perfect push/pull arrangement, it may act like one in a not so efficient way.
But, looking at my HAF X, I think that there is enough clearance for a real push/pull arrangement. Depending on the mobo it may be close and may hang down past it, but there should be clearance to the side (watch out if your mobo has high heat sinks). At best I think it would be a tight fit but doable.
I think I saw a video on it also. Will try to find it and post here.
Inside mounted push/pullhttp://www.youtube.com/watch?v=BbH1mhZWRn8
And a little different 2 push from inside and 2 pull from the outside the casehttp://www.youtube.com/watch?v=m3qC6taRslQ&NR=1