I was leery of the Kingwin/Superflower names - they do sound like plastic toy makers - but the
units do review very well. People have had samples with issues, but the same goes for almost every other name in the business when it comes to the high efficiency models (and especially the generic brands and their budget models).
The thing about hi-power (.7-1.0 kW) units is you're wasting money (and precious resources, if you think about it) on components and circuitry you will never utilise. Efficiency at different loads is pretty much a moot point nowadays with the flat curves the 80 Plus certification guarantees, but there is still a point to that, which I shall demonstrate with the following graphic:
That's the PSU I use. Pretty flat right, there's like a 4 percentage point variation in that, can't be too many watts in a PSU rated for 530 W. This is what the 80 Plus spec was made for, consistency, besides raising the efficiency baseline. Now what's noteworthy here is how the graph line only starts after 20%.
This is because the 80 Plus certification starts at 20% rated wattage, i.e. they guarantee the proper efficiency from that point onwards.
As edh pointed out, your power consumption, as well as the consumption of most modern desktops, will typically be at or around 100 W, even less than that for systems that have more mainstream GPUs. This means that most of the time (what
typical means), your PSU is working outside any sort of certified efficiency range. 80 W would be 10% of 800 W, which is just ridiculous. As for the peak, 300 W sounds about right; the card has been tested to have a 180 W absolute-torture-test-maximum draw, and your CPU should have around a 110 W absolute-100%-load-maximum. The other components in your system have draws in the single digits.
Even if we consider gaming, you're not looking at peak draw. Judging by the Techpowerup review of the card, you'll find it eating up some 150-160 W in graphics-heavy games, whereas your CPU will hardly be 100% loaded. The 250 W edh estimated is probably not far off at all.
250-300 W from an 800 W rated PSU doesn't even reach 50% of the rating. You don't need the power reserve for gaming, for torture tests or future-proofing. It's just waste, quite literally in a sense.
PS. The
Sabertooth is a big waste of money. It's a popular choice because people fall for the hype, but the reviews have found it lacking, and the "armour" to even be detrimental. I would switch to mATX if possible, if you're only going to have 1 or 2 cards in the system. Compact rigs are arguably nicer to live with, and the P8Z77-M Pro I've been very happy with would save you close to $100 (which you can put towards a nice(r) case and the fan swap you'll need for the cooler, or you can update that Dell into an Eizo Foris). Also, the WD
Black HDD is going to be noisy - you already have an SSD, so definitely get a Red or Green as your storage drive, much nicer and still plenty quick.
PPS. If we consider the above efficiency curve, it would be pretty fantastic to have typical consumption in the optimal efficiency range and have the best possible efficiency for the highest loads, no? Assuming efficiency is highest around 50% of rated wattage, this would mean the ideal PSU would be 100 W x 2 = 200 W. Since you DO require power reserve for gaming, we have to calculate that as well; the tail end of the efficiency peak being around 60%, this would be 250 W / 0,6 = 416 W. The expected 300 W peaks would still be covered by that rating (341 W output if 80 Plus Bronze). If we assume a degradation of 20% (crazy much) over the product's lifetime, we'd need 376 W of output, i.e. a rated power of 458 W at 80 Plus Bronze spec.
Summa summarum: get a 450-500 W Bronze PSU or shoot for the stars with 400 W Gold/Platinum.
There are plenty of downsides to it and surely there's something more worthwhile you could spend the money on instead?
