if its really old and making noise, its time for a new psu. i would suggest you go with antec, seasonic, or XFX and you can get a good quality 450 or 550 watt psu for under $50. and the 7790 is better.
I will go for GTX560Ti because it's cheaper.
Which one of cheapest ones do you recommend from seasonc, antec or xfx?