The Q701 definitely has more bass than the AD700, especially subbass! It can actually kick and rumble, unlike the AD700. It doesn't sound bass-light with "natural" sounds and real recordings, but it kinda falls behind when it comes to synthetic stuff. I actually like it for some of my technoey music, such as 'Infected Mushroom' because the bass never gets in the way. It's fast and tight, yet still punchy. In addition to some more bass, you will get a lot more treble though. I hope you don't mind more shimmer and sparkle^^.
The Fidelio X2 is completely different. Its bass is the main thing. It is POWERFUL. It's fantastic for gaming and movies, because it can really rumble. But at the same time, the mids and treble are there, nice and clear. The bass comes first, then the treble, and finally the mids. So its frequency response curve is "U-shaped." Its best thing, besides the bass, is its soundstage. It is at least as big as the AD700's. It's amazing!
Q701 soundstage might sound more 2D at first. But it sounds very sharp, very defined. And it IS fantastic for gaming, as forum member Mad Lust Envy says.
If you just want more bass, go for the Q701. It has all the bass.
But if you want fun, exciting bass, go for the X2.