is my 750w PSU enough for the GFX cards I want?

The recommended manufacture settings for any kind of graphics card is generally 550W as a minimum for a PSU; for a singular card for your card; it is more than enough. With 2 in SLI mode; it depends.

As long as you do not upgrade any other components except for the graphics card; it should be fine; now in saying so; I believe you should look into upgrading the stock CPU cooling fan as well as both of your graphics cards with an aftermarket heat sink.

The reason why I am suggesting this, is to reduce your overall ambient temperature; because the CPU will normally run around 50 degrees inside the case, that's 50 degrees Celsius and with your two graphics cards; if they do not have adequate cooling; will operate approximately 70 degrees Celsius each. If the case you are using does not have adequate cooling; your system will overheat and you will receive lots of PSODs (Pink Screen of Death) instead of BSODs; and thus increase the overall heat inside the system; place a load of stress on your components; and draw more power than needed to cool your system.

For any gaming requirements for any one; I would definitely without a doubt recommend in upgrading the stock cooling fan for the CPU and graphics card(s); as it will reduce the stress load on your components, allow your system to run properly without fault; as well as to keep your power usage to optimum levels.

After you have made this upgrade; try the two video cards and see what happens from there; if it struggles to run both of them; then perhaps upgrading the PSU from there to may be an 850W.

My OPINION:

I don't think so since it needs a minimum of 500w for each. I'm guessing it would work until you run something heavy so your system won't have enough power. That might either cause visual defects in-game or cause your system to shut down completely if it REALLY lacks power. I have have only 1 Zotac gt220 on a 300W PSU (which is minimum) and it runs fine. Only thing is that it used to (for the first month) crash, completely closing any video/game I was running. It stopped now, so might just be the drivers

What I dug up while looking for info:

500w is the minimum RECOMMENDED amount. The cards don't actually draw that much. The regular ones draw 170w. Your other components, of course, draw some power as well. You could check this page to confirm: http://www.overclock.net/nvidia/993912-gtx-560-ti-...

What I think you should do:

Go for it! I know what it's like to have a new working graphics card. Plus what was written on my gt220's box was 520Mb and it turned out to be a 1Gb. It still runs super well now. I've had it for a year and I'm playing crysis 2 on it (Minimum settings of course). Apart from the first month, it has never failed. I don't see why yours should.

Its more than enough,

The minimum PSU requirement set by Nvidia is 500 watts but this is not for the graphics card alone but encompasses the whole system based on the average hardware a computer might have and then adding 50 to 100 watts as a buffer.

So given that 500 watts is minimum for one card and other hardware and a second card will consume 170watts at max it equalls a minimum 670watt PSU.

Run this PSU calculator http://extreme.outervision.com/psucalculatorlite.j... I ran it with the limited hardware you listed and guessed a few and came up with a power consumption of just over 500watts

If this pc is merely a extreme end gaming laptop, then i will make some strategies. X79 is for workstations. Gaming are no longer in a position to apply hyperthreading, so i7 processors are a waste. Get an i5 3570k quad center, socket 1155. As for ram, 2 4gb sticks is greater advantageous than sufficient, and which you would be able to desire to enhance to 16gb without undertaking. The samsung ssd is amazingly quickly, yet a 120gb would desire to be sufficiently enormous, they are to your working strategies-set and alertness storage. positioned a cutting-edge interest on it for quicker loading events. the different media would desire to be located on a familiar hdd. lots of the gaming overall performance is from the photographs card, a 560ti is okay yet there are severely greater effective playing cards. make advantageous benchmarks for video games you opt to play yet i reccomend a gtx 670, its very virtually equivalent to the greater extreme priced gtx 680. ( As close as 3 fps distinction at inventory speeds) if your choose greater performance, purchase yet yet another gtx 670 for sli. Its now no longer available to tell although in spite of an overclocked i5 and a pair of gtx 670s, a great 850w potential furnish would be merely suitable to your technique.