10 hours ago, westman said:

the I9 7920X 2 x 1080ti seen peaks 950W on a kill-a-watt

Wow is that over clocked?

22 hours ago, ckyliu said:

Yeah on my linked spec I suggest a £75 Corsair TXM650M because it was £65 for the 550W version (both are Gold rated semi-modular).

I suppose by that logic I could've specified the £80 750W but then I was concerned it would be quite lightly loaded and efficiency would suffer as I estimate without overclock and peripherals the system would pull about 330W peak; modern hardware is really a lot more energy efficient.

 

Lightly loaded isn't an issue. As I mentioned, peak efficiency is usually around the middle, but only by a fraction. High efficiency extends quite a way below midway and right up to the high end of the curve these days. 

 

Below is my PSU's efficiency curve. You can see that right down to 200 watts its still 92% efficient. And at 750 watts it's still at 92%. Peak is at 350 watts at 93%. It only starts to drop of rapidly at 100 watts. The other point is that the saving on your electricity bill from such a minuscule variation in efficiency is barely measurable. If it's gold rated or above, then where you are in the curve isn't an issue. 

 

https://www.tomshardware.com/reviews/evga-supernova-750-p2-platinum-psu,4566-5.html

 

 

Fair point, especially since we run a proper voltage rather than weedy 110V

Thanks everyone.  I will definitely take your suggestions on board when deciding on a system.

Have a great weekend.

James

Oops we sort of hijacked your post @JamesGrf - let us know what you decide on the final system specifications!