i have a big doubt, I going to buy a new Gpu Zotac GeForce GTX 660 Ti AMP Edition and the Minimum PSU Requirement is 600 Watt but I don't know if my PSU Ultra LSP750 750-Watt is enough for working correctly with this zotac amp edition and the whole system? because some people say that psu only have 500w real and not 750w its true or false?
For a system using a single GeForce GTX 660 Ti graphics card NVIDIA specifies a minimum of a 450 Watt or greater system power supply that has a maximum combined +12 Volt continuous current rating of 24 Amps or greater and that has at least two 6-pin PCI Express supplementary power connectors.
Total Power Supply Wattage is NOT the crucial factor in power supply selection!!! Total Combined Continuous Power/Current Available on the +12V Rail(s) rated at 45°C - 50°C ambient temperature, is the most important factor.
Overclocking of the CPU and/or GPU(s) will require an additional increase to the maximum combined +12 Volt continuous current ratings, recommended above, to meet the increase in power required for the overclock. The additional amount required will depend on the magnitude of the overclock being attempted.
The Ultra LSP750 750-Watt Power Supply (ULT-LSP750), with its maximum combined +12 Volt continuous current rating of 45 Amps and with one 6-pin and one (6+2)-pin PCI Express supplementary power connectors, is way more than sufficient to power your system configuration with a single GeForce GTX 660 Ti graphics card.
It's not considered a very reliable power supply unit though. It looks like it's based on an older discontinued Andyson 700 Watt platform.