Well, that FSP Hexa+ isn't a great unit and uses cheap caps. If it's new it's probably not as likely to be the problem as some even lower quality models, but still possible. If it's used, it's much more likely to be the problem. If you bought that unit from that shop in addition to the GPU card, I'd stop going to that shop. No reputable shop would recommend such a unit for use with a high end gaming card.
The GTX 560 is MANY generations old, so even if it had never been used before it would be a terrible choice. The fact that it's used is definitely a concern and considering the shop sold you a HEXA+ unit WITH that GPU card, tends to lead me to believe that perhaps they bamboozled you on that card and knew it had a problem, or due to it's age it simply failed.
Since your beep code indicates RAM, and they don't beep that way unless there is at least SOMETHING related to the code that's being reported, I'd focus my attention on the memory, or the power supply not providing enough power for the memory. Since the integrated graphics isn't working either, that pretty well eliminates the GPU card. Try each memory module individually in the slot designated for operating when using only a single module according to the motherboard manual. Using other population rules may not allow the system to POST on many systems.
Keep in mind that the PSU could cause the RAM to throw errors. Maybe try the other PSU you replaced to see if the system boots with just integrated graphics. If so, take the PSU back.