I don't know if I need to electrician to be able choose a good PSU , with all the letters and number together +12V -12v 18A .. All this only reminds me of Intergral calculas. I don't understand it and as far as my GPU goes , it recommends a 450w Power supply but when I use eXtreme power calculator I came upto only 268 W . Now I'm confused.
The build includes
AMD Athlon 7750(2.7ghz)
ATI Radeon 4850
DVD/CD RW combo
Corsair XMS2 800mhz
Will a 350 watt Corsair do for all this and overclocking the 7750 to 3 ghz? . Is Corsair the best in PSU?
It has a 30 amp 12 volt rail. That is certainly good enough. Figure that a 350 watt Corsair would have about a 25 amp 12 volt output. That's a little close for my taste.
My SWAG (scientific wild assed guess) for your power consumption:
CPU - OC'd: 8 amps @ 12 volts = 96 watts
GPU - 9 amps @ 12 volts = 108 watts
HD - figure 1 amp at 5 volts & 1 amp at 12 volts (labels will say a little less) = 17 watts
DVD - 1.5 amps @ 5 volt & 2amps @ 12 volts = 30 watts
2GB RAM - 3 amps @ 3.3 volts = 10 watts
MB - 3 amps @ 5 volts & 1 amp @ 12 volts = 27 watts
Fans - 1 amp at 12 volts = 12 watts
I get about 280 watts. Keeping in mind that I rounded upward in a couple of places, the eXtreme power calculator pretty closely agrees with me.
Video card manufacturers always overestimate power needs. For one reason, they cannot assume that you are going to select a good PSU. They have to assume that some people are going to select something like the Rosewill's.
I prefer to operate my power supplies at between 50% and 70% capacity. Your system would load a 350 watt PSU at about 80% of capacity. That's well within specs and the specified 80% efficiency, but as I said, I would prefer a 400 - 450 watt PSU.
And, yes, Corsairs are top bracket PSU's throughout the whole line.