To expand on what I was saying earlier, I would personally spend a bit more cash on the 970 for the serious performance gains, but the 770 is a solid card. More than enough to push WoW and Battlefield (I use one).
It's up to you whether or not you want to spend well outside of your budget to get the 970. Was just saying what I would do, but I've been running this 680 for a while so I just want to upgrade.
The Newegg build videos to teach you how to build a PC.