Your system probably draws 250W max if everything is at stock clocks. A 9600gt draws 70W at most. 483W is ridiculous and that is the exact reason you should take these online calculators with a grain of salt.
There are three main rails in a PSU: 3.3V, 5V and 12V. Modern computers are 12V heavy. That means that a normal setup only uses a few amps on both the 3.3V and 5V. The CPU and GPU both run on 12V and are the most power hungry. When manufacturers go to rate their PSUs, they should be rated with a modern 12V heavy system in mind. In most good, modern PSUs the 3.3V and 5V rail shouldn't account for much mroe than ~50W of the total rating. For example, the Corsair cx400 has 30A on the 12V. 30A of 12V is 360W. Add ~50W to 360W and you come to the ~400W figure. That is based on realistic rail usage. Older computers were more 5V heavy. PSUs with large 3.3V and 5V capacity compared to the 12V are intended for older computers where the CPU was run on 5V. If a modern PSU is sold with a layout like that it means they are trying to inflate their overall wattage since very little of the 3.3V and 5V rails will be used.
And, I am not sure what you mean by this:
Originally Posted by RUGRLN
Had a look at Antec's PSU and I see even the 500W NeoPower has more than 15A per 12V so like 30A+...do you believe this is affecting the performance of GFX card in anyway?
The NeoPower 500W has 38A combined on the 12V. That 38A goes to wherever it is needed, up to the 17A limit for each rail. 17A on a rail is more than enough to power any video card that a 500W PSU is intended to run. And to be confusing, even though these Antecs are labeled as multi-rail units they are in fact a single rail. The rails have been joined together, to put it simply, to make one larger 38A rail.