THe antec is £48 from ebuyer and OCZ is £45 from ebuyer
I divided the Watts by the 12V on both and antec gives 30A and OCZ gives 40A i think. Although OCZ has 70watts more and more amps, some people online say antec is better but i am not too sure on that one. I think i need 30A for my hd4850 and tbh if antec is running at 80% then its going to be too low for me anyway? ( even tho i costs more!)
I only plan on having x1 HDD or 2 max so i am not fazed by the x2 sataII connectors or whatever.
Your system will be find with either. Get the cheapest. It will be more than enough power.
That is not how you calculate the Amps on the +12V rails because the wattage includes the other rails. If it only included the +12V rails then the Wattage is all you would need to look at. To find out the amps on the +12v rails you will need to find a chart from the manufacturer or look on the back of the box. Then look to see what they wrote as the wattage for the combines +12V rails only. I think you also fail to realize the Watts and amps are directly related. P=IV. In otherwords power (watts) is equal to amps multiplied by voltage.
The Antec has 17A on the first +12V rail and 16A on the second. The OCZ has 18A on each of its two +12V rails. I cannot find the actual wattage but I assume it will be between 300 and 400W for both, with the OCZ providing more power which is more than enough for your system.
Hard drives have very little power draw (less than 10W each).