The only thing in your computer that, if blows, has the potential to take everything else down with it is the PSU. Its a risk you take when taking an unknown PSU, and from what little research I've done on rocketfish it all points to being a definite risk, issues with sub par PSU's can range from power up issues, components not working to there potential and just an all out blowout and then you can wave goodbye to your other components as well.
Best advice i ever got was not to cheap out on a PSU, purchase a good one and you can re-use it again and again in loads of different rigs, buy a cheap one and take on the risk of having issues all the time, I'm talking from exp here as well, first build I did I had an unknown PSU and I had all sorts of issues until eventually i gave in, went and researched a good PSU and never looked back
560ti will run 1600x900 on BF3 at ultra comfortably, possibly even some AA in there. a 560 wouldn't be far off that at all but its not the best card for its price, I'd go for a 6850 and spend a bit more on a decent PSU.
http://www.newegg.com/Product/Produc...82E16814121419
as an example 6850, good price and good performance
EDIT: Stretch to a 6870 if you can, still cheaper then a 560ti and similar price to a 560.