Since I realized that putting two 780tis in with my i7-920 is not practical in price or performance. I am thinking about getting a GTX 770. The only thing I am skeptical about is if it would work fine with a 575 watt psu.
The same thing i7Baby recommended. I have so far not had any stability issues, or any issues for that matter. I've had the rig for about a month (Tomorrow would make it a month)