I can't say anything from experience (yet) but from what I've learned the Philips Fidelio X2's are going to be your best bets. It seems like you're a gamer (like myself), and I can say that you've picked a good sound card (I want the Z, but it doesn't work on Linux, so I'm looking at alternatives ATM). The X2's are the new version of the X1, and the X2's have just now been released. Depending on where you live, you might not even be able to get them. No matter what you get, you'll be able to power it with your card, so you don't have to worry about that. I can recommend checking out
http://www.head-fi.org/t/534479/mad-lust-envys-headphone-gaming-guide-update-10-15-2014-beyerdynamic-t51i-added
That right there. Pretty good reviews on stuff, gives you an idea as to what you're getting. Remember, the X2 is brand new, and it's hard to find stuff on right now, but if you're in America you can purchase it here (I will be buying it from here very soon)
http://www.amazon.com/Philips-X2-27-Fidelio-Headphones/dp/B00O2Y2MZG/ref=sr_1_1?ie=UTF8&qid=1413483925&sr=8-1&keywords=philips+fidelio+x2
If you're not in America, it's a bit easier to find it for most countries. As I said, brand new and all.
There's a few reviews out there, but to save you the trouble, here's the differences from the X1:
Better low impedance cable, so less interference/white noise
Accommodation for larger heads
Removable ear pads
Better, more refined bass (NOT louder, more prominent, etc, but instead better in quality and effect;aka better bass experience overall)
Few other things too, but sound hasn't been changed a whole lot. Still changes to it, but mostly the bass.
If you get the X1's, note that the top headband will not be large enough for those with rather large heads. Plus, if you get the X1's, you're GOING to get a new cable. The cable that comes with them has a large impedance, thus ruining the point of good audiophile grade headphones. You can get pretty good ones for ~10 bucks from what I hear.
The Q and K 701's are known to have a sound stage "too big" at times, as it sounds fake and distant from what I've heard
The 598's are a really good choice, however their bass isn't quite there. They're a really neutral headset, nice soundstage, but their bass loses it's.. bassyness... It's just not punchy from what I hear.
Whatever you get, let me know. I'm interested to see how you like it.
But can you do me something? Let me know how well you like that mic that comes with the Sound Blaster Zx. I'm getting the Z, so I won't have quite as good of a mic, but I'm getting a very similar mic to yours, therefore I am interested in it's quality. I hear it's pretty good, and is fantastic for a freebee. I'd really appreciate your thoughts on it. Thanks.