I recently took back my old GPU because of crashes and got this to "Fix" it. But now it crashes on some games, but unlike the last card it does it randomly, i got blue screen erliar and it crashes quite often, its only majorly crashed on Just Cause 2, BF4 multiplayer and Rust.... I think it may be my powersupply, its 550W but its pretty bad, it was kinda cheap like £45 or something, so i think it might be that.
I have a GTX 660 as well, and I had encountered a similar issue where it would crash. MSI Afterburner is a great program to monitor your GPU with. It's a good idea to have a reasonable power supply, and make sure to check your power options aren't set to "power saver". Your system locks up if it doesn't have a decent PSU.